A=g≈-32
v=⌠a dt since a≈-32
v=-32t+C, where C is the initial velocity, which we are told is 20 ft/s
v=-32t+20
h=⌠v dt
h=-32t^2/2+20t+C, where C is the initial height, so what is a reasonable initial height? How about 3 ft since we are swinging a bat around maybe our waist level... maybe :P
h=-16t^2+20t+3
Your choices may have made a different assumption about the initial height of course but you did not show your choices, but certainly it will be:
h(t)=-16t^2+20t+hi, where hi is the initial height in feet.
This of course ignores air resistance and flight dynamics of a spinning ball with seams, which will make a significant difference in real life :)
Answer:

Step-by-step explanation:
We are given:

![interval = [a,b] = [0,2]](https://tex.z-dn.net/?f=interval%20%3D%20%5Ba%2Cb%5D%20%3D%20%5B0%2C2%5D)
Since
⇒ 
Riemann sum is area under the function given. And it is asked to find Riemann sum for the left endpoint.

Note:
If it will be asked to find right endpoint too,

The average of left and right endpoint Riemann sums will give approximate result of the area under
and it can be compared with the result of integral of the same function in the interval given.
So, 

Result are close but not same, since one is approximate and one is exact; however, by increasing sample rates (subintervals), closer result to the exact value can be found.
The answer should be 6,000
Answer: -4x -8
See picture below for step by step