using the range of estimates method provide a solution

An earthmoving contractor is evaluating whether to use a larger excavator to rectuce current operating costs. The excavator can be purchased at $135,000 and is expected to have a usefur ilite of 5 years after which it can be sold for $25,000. The optimistic, most ilikely, and pessimistic profections of annual savings in operating costs are $40,000,$30,000, and $14,000, respectively. Use the cunte of estimates method to compute the mean annual savings, and then determine the present worth of purchasing this excavator at 7% interest