$Q={?}_{?}$ A company plans to purchase new cut$-$and$-$finish equipment. Two manufacturers offered the estimates below.

$\backslash$table$[[$Description$,$Vendor A$,$Vendor B$],[$Initial Cost $($$$),15000,18000],[$Annual Operating Cost $($$$),3500,3100],[$Salvage Value $($$$),1000,2000],[$Life$,6,9]]$

$($a$)$ Determine which vendor should be selected on the basis of a present worth comparison, if the MARR is $15\%$ per year.

$($b$)$ The company has a standard practice of evaluating all options over a $5-$year period. If a study period of $5$ years is used and the salvage values are not expected to change, which vendor should be selected?