$M(N,R)=\frac{N}{R}$

A certain company pays a tax rate of $30\%$ on its income.

$($a$)$ Use I for the income before taxes, and express the net income $N$ in terms of I. $($Be careful: $N$ is the part of I left after taxes$-$not the part you pay in taxes.$)$

$N=$

$($b$)$ Use a formula to express the net profit margin in terms of the variables I and $R.$

$M=$