A Student Gets a Part Time Job Selling Magazine Subscriptions $\$ 36$

A student gets a part time job selling magazine subscriptions. He is paid $\$ 36$ for a 5-hour shift. He also earns $\$ 3$ for each subscription sold. Create a function $\mathrm{f}(\mathrm{x})$ for the amount he earns on a shift when he sells $\mathrm{x}$ subscriptions. Use the function $\mathrm{f}(\mathrm{x})$ to determine how much he earns on a shift that he sells 12 subscriptions.

A) $f(x) =5 x+36 ; \$ 96$
B) $f(x) =3 x+36 ; \quad \$ 72$
C) $f(x) =36 x+3 ; \$ 435$
D) $f(x) =3 x+180 ; \$ 216$