Answer

First we find the value of the integral:

To explain what the integral represents in the language of the problem, we need to know units for t and units for the integral. We're told that t is measured in hours and v(t) in miles per hour. This means the integral is measured in miles. So

is the distance Bob drove from time t = 0 hours to time t = 2 hours. Since we're told 3pm corresponds to t = 0, t = 2 corresponds to 5pm. Putting everything together,

is the distance Bob drove from 3pm to 5pm.