What is the formula to solve this? and How do you get the right calculations? I thought mine was correct, how do I solve this?

June Co. is evaluating a project requiring a capital expenditure of $620,000. The project has an estimated life of four years and no salvage value. The estimated net income and net cash flow from the project are as follows:

Year Net Income Net Cash Flow

1 $45,000 $200,000

2 $85,000 $240,000

3 $5,000 $160,000

4 $15,000 $170,000

$150,000 $770,000

The company's minimum desired rate of return is 12%. The present value of $1 at compound interest of 12% for 1, 2, 3, and 4 years is 0.893, 0.797, 0.712, and 0.636, respectively.

a.Determine the average rate of return on investment, giving effect to depreciation on the investment. Round your answers to two decimal places __?_____%. (I got 31.05, but it is wrong, I need help to solve)

b.Determine the net present value.

$28,080