I added a 5th letter, F.

I enjoyed doing the problem set yesterday, and since I'd only
made one commit, I thought I'd do three more letters to get
to the four commits for the problemset. I continue to have
a bit of difficulty with taking the perspective of the turtle
to know whether one of the arguments for the circle function
should be negative. I tested it every time I made a change,
primarily when I made a segment and turned, so that I could
quickly adjust if necessary. It ended up going pretty quickly!

typeface.py

@@ -65,7 +65,34 @@ def draw_letter_e(unit):
     pass
 
 def draw_letter_f(unit):
-    pass
+    #print(heading())
+    #print(pos())
+    circle(unit,90)  
+    forward(6 * unit)
+    circle(unit,90) 
+    right(180)
+    forward(7 * unit)
+    right(90)
+    forward(2 * unit)
+    circle(-unit,-90) 
+    left(180)
+    forward(3 * unit)
+    left(90)
+    forward(2 * unit)
+    left(90)
+    forward(4 * unit)
+    right(90)
+    forward(2 * unit)
+    circle(-unit,-90) 
+    left(180)
+    forward(3 * unit)
+    left(90)
+    forward(3 * unit)
+    circle(unit,90)  
+    left(180)
+    forward(4 * unit)
+    right(180)
+
 
 def draw_letter_g(unit):
     pass
@@ -77,8 +104,8 @@ def draw_letter_i(unit):
     pass
 
 def draw_letter_j(unit):
-    print(heading())
-    print(pos())
+    # print(heading())
+    # print(pos())
     left(90)
     penup()
     forward(8 * unit)