Given $f(x)=-x^{2}3x4,$ estimate the area under $f(x)$ from $x=0$ to $x=2$ using a Left Riemann sum with four intervals. Please include the following steps in your calculation:

a$)$ Determine the width of the individual intervals

b$)$ List which input values will be used for the heights

c$)$ Give a calculation step that shows width times sum of height values

d$)$ Calculate the final area estimate

$2$ points each for parts a and $d$

$3$ points each for parts $b$ and $c$

$($this question is worth $10$ possible points$)$