Suppose You Have a Firm in Which the Owner Pays

Suppose you have a firm in which the owner pays $10,000 per month on rent of the plant and equipment and will pay that regardless of much output they produce, and once they get going they need $10 in materials and $20 in labor for everyone they produce,

A) Their variable costs are $10,000 plus $10 per unit.
B) Their fixed costs are $10,000 and variable costs are $20 per unit.
C) Their fixed costs are $10,000 and variable costs are $30 per unit.
D) Their fixed costs are $10,000 and $10 per unit.