How do I calculate the contribution Margin for alternative $1?$

Contribution Margin Ratio $=\frac{\text{\$}150,000-\text{\$}45,000}{\text{\$}}150,000=0\mathrm{.}7$

Contribution Margin $=($$$62,500**0\mathrm{.}7)-$$$75,000=$$$31250$

Contribution Margin per unit $=$ Contribution Margin $\frac{?}{?}$ Units Sold $=\frac{31250}{62},500=$$$1\mathrm{.}00$ per unit