diff --git a/projects/01/And.hdl b/projects/01/And.hdl
index ebe08d3..dcd7f2d 100644
--- a/projects/01/And.hdl
+++ b/projects/01/And.hdl
@@ -9,6 +9,8 @@
  *       0 otherwise
  */
 
+// COST = 2 NAND Gates
+
 CHIP And {
     IN a, b;
     OUT out;
diff --git a/projects/01/And16.hdl b/projects/01/And16.hdl
index b9af92e..a40de60 100644
--- a/projects/01/And16.hdl
+++ b/projects/01/And16.hdl
@@ -8,6 +8,8 @@
  * for i = 0..15: out[i] = (a[i] and b[i])
  */
 
+// Cost = 32 NAND Gates
+
 CHIP And16 {
     IN a[16], b[16];
     OUT out[16];
diff --git a/projects/01/DMux.hdl b/projects/01/DMux.hdl
index 68d5376..e965829 100644
--- a/projects/01/DMux.hdl
+++ b/projects/01/DMux.hdl
@@ -9,6 +9,8 @@
  *          {0, in} if sel == 1
  */
 
+// COST = 5 NAND Gates
+
 CHIP DMux {
     IN in, sel;
     OUT a, b;
diff --git a/projects/01/Mux.hdl b/projects/01/Mux.hdl
index 78d2b09..7497430 100644
--- a/projects/01/Mux.hdl
+++ b/projects/01/Mux.hdl
@@ -9,6 +9,8 @@
  *       b otherwise
  */
 
+// COST = 8 NAND Gates
+
 CHIP Mux {
     IN a, b, sel;
     OUT out;
diff --git a/projects/01/Not.hdl b/projects/01/Not.hdl
index 831282a..81dbba3 100644
--- a/projects/01/Not.hdl
+++ b/projects/01/Not.hdl
@@ -8,6 +8,8 @@
  * out = not in
  */
 
+// COST = 1 NAND Gate
+
 CHIP Not {
     IN in;
     OUT out;
diff --git a/projects/01/Not16.hdl b/projects/01/Not16.hdl
index 56d3438..81a3e4c 100644
--- a/projects/01/Not16.hdl
+++ b/projects/01/Not16.hdl
@@ -8,6 +8,8 @@
  * for i=0..15: out[i] = not in[i]
  */
 
+// COST = 16 NAND Gates
+
 CHIP Not16 {
     IN in[16];
     OUT out[16];
diff --git a/projects/01/Or.hdl b/projects/01/Or.hdl
index 8fec4da..7281966 100644
--- a/projects/01/Or.hdl
+++ b/projects/01/Or.hdl
@@ -11,6 +11,8 @@
 
 // Or/Xor: These functions can be defined in terms of some of the Boolean functions implemented previously, using some simple Boolean manipulations. Thus, the respective gates can be built using previously built gates.
 
+// COST = 3 NAND gates
+
 CHIP Or {
     IN a, b;
     OUT out;
@@ -18,6 +20,5 @@ CHIP Or {
     PARTS:
     Not(in=a, out=na);
     Not(in=b, out=nb);
-    And(a=na, b=nb, out=nout);
-    Not(in=nout, out=out);
+    Nand(a=na, b=nb, out=out);
 }
diff --git a/projects/01/Or16.hdl b/projects/01/Or16.hdl
index 4148097..03e7e68 100644
--- a/projects/01/Or16.hdl
+++ b/projects/01/Or16.hdl
@@ -10,10 +10,64 @@
 
  // Or/Xor: These functions can be defined in terms of some of the Boolean functions implemented previously, using some simple Boolean manipulations. Thus, the respective gates can be built using previously built gates.
 
+// COST= 48 NAND Gates
+
 CHIP Or16 {
     IN a[16], b[16];
     OUT out[16];
 
     PARTS:
 
+    Nand(a=a[0], b=a[0], out=na0);
+    Nand(a=a[1], b=a[1], out=na1);
+    Nand(a=a[2], b=a[2], out=na2);
+    Nand(a=a[3], b=a[3], out=na3);
+    Nand(a=a[4], b=a[4], out=na4);
+    Nand(a=a[5], b=a[5], out=na5);
+    Nand(a=a[6], b=a[6], out=na6);
+    Nand(a=a[7], b=a[7], out=na7);
+    Nand(a=a[8], b=a[8], out=na8);
+    Nand(a=a[9], b=a[9], out=na9);
+    Nand(a=a[10], b=a[10], out=na10);
+    Nand(a=a[11], b=a[11], out=na11);
+    Nand(a=a[12], b=a[12], out=na12);
+    Nand(a=a[13], b=a[13], out=na13);
+    Nand(a=a[14], b=a[14], out=na14);
+    Nand(a=a[15], b=a[15], out=na15);
+
+
+    Nand(a=b[0], b=b[0], out=nb0);
+    Nand(a=b[1], b=b[1], out=nb1);
+    Nand(a=b[2], b=b[2], out=nb2);
+    Nand(a=b[3], b=b[3], out=nb3);
+    Nand(a=b[4], b=b[4], out=nb4);
+    Nand(a=b[5], b=b[5], out=nb5);
+    Nand(a=b[6], b=b[6], out=nb6);
+    Nand(a=b[7], b=b[7], out=nb7);
+    Nand(a=b[8], b=b[8], out=nb8);
+    Nand(a=b[9], b=b[9], out=nb9);
+    Nand(a=b[10], b=b[10], out=nb10);
+    Nand(a=b[11], b=b[11], out=nb11);
+    Nand(a=b[12], b=b[12], out=nb12);
+    Nand(a=b[13], b=b[13], out=nb13);
+    Nand(a=b[14], b=b[14], out=nb14);
+    Nand(a=b[15], b=b[15], out=nb15);
+
+    Nand(a=na0, b=nb0, out=out[0]);
+    Nand(a=na1, b=nb1, out=out[1]);
+    Nand(a=na2, b=nb2, out=out[2]);
+    Nand(a=na3, b=nb3, out=out[3]);
+    Nand(a=na4, b=nb4, out=out[4]);
+    Nand(a=na5, b=nb5, out=out[5]);
+    Nand(a=na6, b=nb6, out=out[6]);
+    Nand(a=na7, b=nb7, out=out[7]);
+    Nand(a=na8, b=nb8, out=out[8]);
+    Nand(a=na9, b=nb9, out=out[9]);
+    Nand(a=na10, b=nb10, out=out[10]);
+    Nand(a=na11, b=nb11, out=out[11]);
+    Nand(a=na12, b=nb12, out=out[12]);
+    Nand(a=na13, b=nb13, out=out[13]);
+    Nand(a=na14, b=nb14, out=out[14]);
+    Nand(a=na15, b=nb15, out=out[15]);
+
 }
diff --git a/projects/01/Or16.out b/projects/01/Or16.out
new file mode 100644
index 0000000..8664afe
--- /dev/null
+++ b/projects/01/Or16.out
@@ -0,0 +1,7 @@
+|        a         |        b         |       out        |
+| 0000000000000000 | 0000000000000000 | 0000000000000000 |
+| 0000000000000000 | 1111111111111111 | 1111111111111111 |
+| 1111111111111111 | 1111111111111111 | 1111111111111111 |
+| 1010101010101010 | 0101010101010101 | 1111111111111111 |
+| 0011110011000011 | 0000111111110000 | 0011111111110011 |
+| 0001001000110100 | 1001100001110110 | 1001101001110110 |
diff --git a/projects/01/Xor.hdl b/projects/01/Xor.hdl
index af2d2d6..8fb7bda 100644
--- a/projects/01/Xor.hdl
+++ b/projects/01/Xor.hdl
@@ -7,6 +7,8 @@
  * Exclusive-or gate:
  * out = not (a == b)
  */
+// Cost = 6 NAND Gates
+// TODO: Improve this
 
 CHIP Xor {
     IN a, b;