engineering economics: construct the cash flow diagram

A father wants to deposit an unknown lump-sum amount into an investment opportunity 2 years from now that is large enough to withdraw P4000 per year for state university tuition for 5 years starting 3 years from now.
•If the rate of return is estimated to be 15.5% per year, construct the cash flow diagram.

Draw a horizontal time line from 0 to 8, the numbers in your timeline represents the number of years. At year 2, draw a downward arrow and labeled it P2. We let P2 stands for the lump-sum amount to be deposited by the father 2 years from now. At time-lines 3, 4, 5, 6, and 7, draw upward arrows, and label each with P4000. From the problem, P4000 is the yearly 5-year withdrawal to be made 1 year after the deposit. Solve for P2 using the formula below.

P2=A[(1+i)n1](1+i)ni

where, A=4000, n=5 and i=0.155

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