Fees and Slippage on a CLOB

How many fills does one pair round trip have?

• Two: one to open, one to close
• Four: open A, open B, close A, close B
• One per leg

A round trip costs $18 on a $6,000 A leg. How far must the spread move in your favour to break even?

• 18 basis points
• 30 basis points
• 3 basis points