Jack buys several articles for $'n'$ costs per dozen and his selling price is $\large\frac{n}{9}$ cent per article. What is the profit in cents on each article ?

Question

$\begin{array}{1 1} (a)\; \large\frac{n}{16 } \\ (b)\;\large\frac{n}{20 } \\ (c)\; \large\frac{n}{36} \\ (d)\; \large\frac{n}{40} \end{array}$