need help with parts a,b,c, and D with work shown to make sure my work is correct. Thank You !

Problem 1 An aircraft company has an order to refurbish 20 jet aircrafts. The work has learning rate 80%. Based on past experience with similar jobs, the company estimates that the first plane will require 350 hours to refurbish. Calculate the following: a. The time estimate for refurbishing the 5th plane b. The cumulative time estimate for refurbishing the first five planes c. The time estimate for refurbishing all 20 planes d. If each worker assigned to this project works 150 hours per month, how many workers should be assigned to this project to complete it in a month