During the first five hours of a lab experiment, the temperature of a solution is given by...

During the first five hours of a lab experiment, the temperature of a solution is given by

where t is measured in hours, t = 0 corresponds to the time that the experiment begins, and F(t) is the temperature (in degrees Celsius) at time t.

(a) Find (and simplify) a formula for ∆F/∆t over the interval [a, 5].

(b) Use the result in part (a) to compute the average rate of change of temperature during the period from t = 4 hr to t = 5 hr. (Be sure to include the units as part of the answer.)