need help with hw prob

Knowing about Economic Equalivalents, someone asks you what one payment in year 4 could you make that would be economically equivalent to all the cash flows below at 6.9% interest? 300 300 300 200 200 250 50 0 1 2 3 4 5 6 7 8 9 10 0 1 2 4 5 6 7 8 9 10