Inactive Tutor answered 05/04/22
This question can be evaluated via a simple integral. First, let's get a rough graph of what we are trying to find.
Essentially, we will be subtracting the area under the red curve(b(t)) from the area under the blue curve(d(t)) in order to get that middle region. Thus, our integral become a definite integral from 0 to 10 of 2400e0.021t-1400e0.015t with respect to t.
Solving for this integral, we get 10630.52921738025 --> 10631.