A three$-$year$-$old small crane is being considered for early replacement. Its current market

value is $$39,600.$ Estimated future market values and annual operating costs for the next five years are

given in the table below. What is the economic life for this crane if the interest rate is $7\mathrm{.}8\%$ per year?

Year $-$Market Value$-$ Annual Operating Cost

$0-$$$39,600-$

$1-$$$36,710-$ $$3,800$

$2-$$$34,090-$$$3,864$

$3-$$$31,250-$ $$3,954$

$4-$$$29,110-$ $$4,077$

$5-$$$25,000-$ $$4,130$