"If I Didn't Have Class Tonight, I Would Save the $4

Multiple Choice

"If I didn't have class tonight, I would save the $4 campus parking fee and spend four hours at work where I earn $10 per hour." The opportunity cost of attending class this evening is:

A) $4.
B) $40.
C) $44.
D) $0.
E) dependent on the usefulness of the information learned in class.