For the functions in Exercises $39-46,$ find a formula for the Riemann sum obtained by dividing the interval $[a, b]$ into $n$ equal subintervals and using the right-hand endpoint for each $c_{k}$ . Then take a limit of these sums as $n \rightarrow \infty$ to calculate the area under the curve over $[a, b]$
$$f(x)=x^{2}-x^{3} \text { over the interval }[-1,0]$$