Grace Is Headed to Work at a Catering Business as a Waitress

Grace is headed to work at a catering business as a waitress for $100.Her sister Paige calls and asks her to go horseback riding instead.Grace decides to go to work,which implies Grace's opportunity cost of working is:

A) greater than $100.
B) less than $100.
C) equal to $100.
D) Cannot be determined without more information.