${\displaystyle \underset{0}{\overset{1}{}}}(x^3-3x^2)dx$

a$)$ Find a formula to approximate the above integral using $n$ subintervals and using Right Hand Rule. $($enter a formula involving $n$ alone$).$

b$)$ Evalute the formula using the indicated $n$ values.

$n=10$

$n=100$

$n=1000$

c$)$ Find the limit of the formula, as $n,$ to find the exact value of the integral.