Compute the solution of given problem

Problem- During the early morning hours an inversion develops. At 8am the depth of the inversion is 200m and the average wind velocity is 0.5 ms^-1.

Part 1- Calculate the ventilation rate. By 4pm the inversion has essentially dissipated and the mixing depth is now 1500m and the average wind speed is 4.8ms^-1.

Part 2- Calculate the ventilation rate under these conditions.

I want help to find the ventilation rate.