How do I calculate the net present value and the internal rate of return? I thought I did the calculations correctly.

6%
Initial cost	$170,000	$274,000
Annual cash inflows	$72,200	$82,200
Annual cash outflows	$31,400	$26,700
Cost to rebuild (end of year 4)	$50,100	$0
Salvage value	$0	$8,200
Estimated useful life	7 years	7 years
				year	Option A	Option B
				0	($170,000)	($274,000)
				1	$40,800	$55,500
				2	40,800	55,500
				3	40,800	55,500
				4	-9,300	55,500
				5	40,800	55,500
				6	40,800	55,500
				7	40,800	63,700
				IRR	8.97%	10.04%
				PV	$227,761.16	$315,275.64
					($39,683.89)
					$188,077.27
			Total PV		$188,077.27	$315,275.64
				PVI	$18,077.27	$122,700
					1.11	1.45

Sandhill Clinic is considering investing in new heart-monitoring equipment. It has two options. Option A would have an initial lower cost but would require a significant expenditure for rebuilding after 4 years. Option B would require no rebuilding expenditure, but its maintenance costs would be higher. Since the Option B machine is of initial higher quality, it is expected to have a salvage value at the end of its useful life. The following estimates were made of the cash flows. The company's cost of capital is 6\%. Compute the (1) net present value, (2) profitability index, and (3) internal rate of return for each option. (Hint: To solve for internal rate of return, experiment with alternative discount rates to arrive at a net present value of zero.) (If the net present value is negative, use either a negative sign preceding the number eg - 45 or parentheses eg (45). Round answers for present value and IRR to 0 decimal places, e.g. 125 and round profitability index to 2 decimal places, e.g. 12.50. For calculation purposes, use 5 decimal places as displayed in the factor table provided.)