Additional Requirements: 4 buttons

There are two versions of this pattern:

Version 1 uses 2 colors; yarn requirements for each color (# of balls):
Size A: 8 of color A and 7 of color B
Size B: 9 of color A and 8 of color B
Size C: 9 of color A and 9 of color B

Version 2 uses 1 color; yarn requirements (# of balls):
Size A: 15
Size B: 16
Size C: 17