... is PV = [1/(1 + r)] f, where PV stands for present value, r for the rater of interest, and f for future costs or benefits. The interest rate used in this formula is the rate at which we discount ... differential for students in the two programs? READING: The Effect of Airline Deregulation on Travel Safety William F. Shughart II, University of Mississippi Before 19 78 airlines in ... Government Printing Office, 19 98) , table 732. To obtain the total cost of childcare, you must then estimate the value of parental time. 3 The mathematical formula for computing the present value...