Please Help with Problem 20.14 !!

20.13 For a wind speed of 6m/s, a stack gas exit velocity of 20m/s, a stack diameter of 4m, a heat emission rate of 15MW, and an ambient pressure of 950mb, calculate the final plume rise in a neutral atmosphere using (a) the Holland; (b) the modified Concawe; and (c) the Briggs method. Assume the stack gas has a molecular weight of 28.9. 20.14 Rework Problem 20.13 for Class E stability and a wind speed of 3m/s. Assume the ambient temperature is 280K