A business operated at $100\%$ of capacity during its first month, with the following results:

Sales $(120$ units$)$

$$600,000$

Production costs $(150$ units$)$:

Direct materials

$$75,000$

Direct labor

$18,750$

Variable factory overhead

$33,750$

Fixed factory overhead

$30,000$

$$157,500$

Operating expenses:

Variable operating expenses

$$5,700$

Fixed operating expenses

$4,250$

$9,950$

The amount of contribution margin that would be reported on the variable costing income statement is

a$.$ $$492,300$

b$.$ $$590,050$

c$.$ $$599,850$

d$.$ $$488,050$