please help

A project initial cost is I, the present worth of benefit is PWB, the present worth of operation and maintenance cost is PWosm, and the present worth of salvage value is PWs, which of the following formula is the benefit cost ratio? O PWB/(1+PWO&M - PWS) PWB/(1+PWO&M + PWs) O PWB/(1-PWO.M-PWs) O (PWg - PW)/(I - PWOSM) If you are considering making an investment on a financial product which costs $8,628 initially, and pays back $1,549 every year up to 6 years. What is the payback period of this product (keep two decimal places)