Leah Berry Is Entering Her Senior Year as an Accounting

Leah Berry is entering her senior year as an accounting major and has a number of options for her summer break.Her options for the 3-month break follow:
(1) Work full time at a local accounting firm making $3,200 per month.
(2) Take a summer class which will cost $600 and work half time making $1,600 per month.
(3) Take two classes at a cost of $1,200 and not work at all during the summer.
Leah's opportunity cost of taking two classes if she chooses option 3 over option 1 would be

A) $3,200 per month.
B) $2,000 per month.
C) $1,200 per month.
D) $1,600 per month.