A Company Estimates That the Rate of Revenue Produced by an Investment

Short Answer

A company estimates that the rate of revenue produced by an investment will be K(t) thousand dollars per year at time t, where $\mathrm { K } ( \mathrm { t } ) = 9 \mathrm { t } \mathrm { e } ^ { - 0.2 \mathrm { t } }$ Find the present value of this stream of income over the next four years using 10% interest rate.
Enter just an integer (no units) representing the amount to the nearest dollar.