Answer:
Payback is in period 3
Explanation:
We use a cash flow to solve this problem. File with Cash flow is attached.
At moment 0 we have the investment cost , in this case $750,000. From period 1 to period 4, we have different incomes. Then, we calculate the Net cash flow that is the difference between benefits and cost.
Payback is the moment when cumulative Cash Flow are higher than 0. In this case, period 3.