A new van was purchased for $$40,000$ and was estimated to have a life of $4$ years or

$110,000$ miles; trade$-$in $($residual$)$ value is estimated to be $$4,800.$ In the fir year, the

van was driven for $27,500$ miles.

a$.$ Use the unit$-$of$-$production method to determine the depreciation per mile $($unit$).$

b$.$ What is the total depreciation expense for the first year?