A Miscalculation #2

This calculator was purchased at Evergreen Office Supplies.  Smudge reprogrammed it so it gives the following answers:
5 - 1 = 6
5 - 2 = 7
5 - 3 = 8
6 - 1 = 7
What will be the answer if you enter 4 - 3 = ?

a. 7
b. 8
c. 9