Unequal project lives

Galaxy Corp. has to choose between two mutually exclusive projects. If it chooses project A$,$ Galaxy Corp, will have the opportunity to make a similar investment in three years. However, if it chooses project B$,$ it will not have the opportunity to make a second investment. The following table lists the cash flows for these projects. If the firm uses the replacement chain $($common life$)$ approach, what will be the difference between the net present value $($NPV$)$ of project A and project B$,$ assuming that both projects have a weighted average cost of capital of $13\%?$

$\backslash$table$[[$Cash Flow,$],[$Project A$,,$Project B$,],[$Year $0$:$,-$$$20,000,$Year $0$:$,-$$$45,000$