Please help me solve this using excel. The three methods

Iwoukd like to the rate function in excel if possible. Not sure what function for oayback in excel.

I am trying to do$,$ IRR, Payback and am using NPV and inthink i have the NPV method down but would still like to check.

Question below:

In the Wamo$-$Dyne Catalogue, a "Grainger"$-$like catalogue that specializes in laboratory equipment, the list price of the much needed Guanine$-$Adenine$-$ThymineCytosine Nucleotide Splicer, Model XJ $5000$ is $$75,000.$ You're an engineer working for a genome$-$altering biometrics firm and you're in charge of the purchase. $($Lucky you!$)$ However, you're faced with a dilemma: You can buy the equipment directly from GeneSplicers, Inc. $($the manufacturer$),$ but you can't afford the list price. But not to worry, GeneSplicers, Inc. is offering financing at $8\%$ with annual payments for four $(4)$ years and only requires a down payment of $$25,000.$ Alternatively, Hank, the friendly hometown salesman who works for WamoDyne, is offering to sell the equipment for a $10\%$ price reduction from list price if you pay cash today. Your management is asking you to defend your decision three ways$-$they don't care which financial analyses you choose, but they want to see three different methods. With human lives on the line in desperate need of some nucleotide splicing, which alternative will you recommend?