Answer:
(a)
(b)62.85cm
Step-by-step explanation:
The growth rate of the shrub is given as:

Where t=time in years, h=height in centimeters
(a)First, we solve for the height h(t) by integrating.

(b)The shrub are sold after 7 years of growth. Therefore, we determine the value of h(t) when t=7 years.

The Shrubs are 62.85cm tall when they are sold.
Well well we find the area of the triangle first:
area = 1/2 * base * height
area = 1/2 * 8 1/4 * 5 3/4
area = 1/2 * 33/4 * 23/4
area = 1/2 * 759/16
area = 759 / 32
area = 23 23/32
now if we multiply the length of the triangles we get volume because the volume of the prism is really just the sum of the areas of all the triangles that make up it's length. So:
volume = 23 23/32 * 12
volume = 276 276/32
276/ 32 = 8 5/8
volume = 284 5/8