Question $2$

A mechanical engineer must recommend an $\frac{A}{C}$ system to a commercial building

owner. The owner uses and MARR of $6\%,$ but is not sure how long he will own

the building. A conventional split system has a design life of $10$ years, a cost of

$$54,000,$ and annual operating costs of $$15,000.$ A chilled water system has an

initial cost of $$71,000$ and annual operating costs of $$15,000.$ Assuming each

unit has no salvage value and will be identically replaced for the life of the

building, determine how long the chilled water system needs to last for it to be

the best choice $($i$.$e$.$ determine the breakeven useful life for the chilled water system$).$ Express your answer in years to the nearest whole year.

$15$ margin of error $+/-1.$ Why is it $15$ and not $19$ work it out for me please.