Hello can someone double check if I got these right?

Thank you!

If you are considering making an investment on a financial product which costs $8,056 initially, and pays back $1,915 every year up to 6 years. What is the payback period of this product (keep two decimal places)? A project initial cost is I, the present worth of benefit is PWB, the present worth of operation and maintenance cost is PWO&M, and the present worth of salvage value is PWS, which of the following formula is the benefit cost ratio? PWB/(I+PWO&M+PWS)PWB/(I+PWO&MPWS)+(PWBPWS)/(IPWO&M)PWB/(IPWO&MPWS)