please solve with formulas not excell

NAW is the Net annual worth

Problem Group C Periodic and gradient payments. C.1. Assume that 18 months ago the state highway patrol purchased a new airplane for $55,000. Now the plane needs repairs. They need to decide whether to repair the plane and keep it, or trade it in on a new one. The "do nothing" alternative is not available. Whichever plane is se- lected will be kept for the next 60 months and then sold. The costs of each alternative follow: A: Keep and repair B: Trade in on new Market value if sold now, as is $40,000 Repairs needed now 6,500 Dealer's advertised price for new plane $70,000 Trade-in allowance for present plane, as is 48,000 Dealer financing on the difference 22,000 New-plane amortized loan, for $22,000 at 0.75%, 48 months first payment at EOM 1 O & M for the first month (100 hr/mo.) $10.00/hr $8.90/hour Gradient O&M for each succeeding month $0.10/hr/month $0.10/hr/month Periodic overhauls at 4-month intervals, with the first at EOM 6 (geo. grad.) $ 1.000 $ 850 Each periodic OH costs 4% more than the previous one Resale value at EOM 60 $30,000 $44,000 HAPTER 11 Incremental Rate of Return (IROR) on Required Investments 325 (a) Use the equivalent NAW to find the IROR. (Hint: Try 1 percent.) (Ans (Ans. 1.35%). (b) Assume other alternatives are available, represented by C and D. Draw the arrow dia- gram and show which alternative is favored if MARR = 1 %. (Ans. Select C.) 1.4% B B D find 2.2% 1.2% 0.9% 1.2% 1.7% B 1.7% 0.9% 2.2% 0.3% 0.3% D (c) Fill in the table below and show the MARR ranges favoring each alternative. (Ans. > 2.2%-A: none+B; 0.3%C: favors A MARR but > favors B MARR