The function a represents the cost of manufacturing product a, in hundreds of dollars, and the function b represents the cost of manufacturing product b, in hundreds of dollars

7t^2 + 3t + 6

Step-by-step explanation:

The computation of the expression is shown below:

The function describes the manufacturing cost of product A.

a(t) = 5t + 2

Likewise for product B, the manufacturing cost function is

b(t) = 7t^2 - 2t + 4

So if we combined these two, the equation would be presented below

= a(t) + b(t)

= 5t + 2 + 7t^2 - 2t + 4

= 7t^2 + 3t + 6

Hence, the correct option is D