Answer:
A: 
Step-by-step explanation:
Acceleration is second derivative of position, velocity is first derivative. Therefore, the velocity is the integral of acceleration.

Integrate:

V(0)=-5:

Therefore, v(t):

Answer:
<u>The ages of Paul and Selena are 13 and 7 years old.</u>
Step-by-step explanation:
Age of Paul = x
Age of Selena = x -6
Age of Paul and Selena in 15 years:
x + 15 = 4 (x - 6)
x + 15 = 4x - 24
x - 4x = -24 - 15
- 3x = -39
x = 13
<u>Paul now is 13 years old and Selena is 7 years old. In 15 years, Paul will be 28, that is 4 times the present age of Selena.</u>
I've attached a plot of one such cross-section (orange) over the region in the x-y plane (blue), including the bounding curves (red). (I've set

for this example.)
The length of each cross section (the side lying in the base) has length determined by the horizontal distance

between the y-axis

and the curve

. In terms of

, this distance is

. The height of each cross section is twice the value of

, so the area of each rectangular cross section should be

.
This means the volume would be given by the integral