The following information is available for Spruce Corporation for a sales volume of $500$ stereo speakers for the past month:

Total

Per Unit

Sales

$$112,500$

$$225$

Less: Variable expenses

$40,000$

$80$

Contribution margin

$ $72,500$

$$145$

Less: Fixed expenses

$ $17,500$

Net operating income

$ $55,000$

What is the contribution margin ratio?

Select one:

A$.40\mathrm{.}0\%$

B$.54\mathrm{.}4\%$

C$.32\mathrm{.}2\%$

D$.64\mathrm{.}4\%$