solve 0= p^5 (528/5 - 280) + 4 p^4(1-p) (528/4 - 280) + 6 p^3(1-p)^2 (528/3 - 280) + 4 p^2(1-p)^3 (528/2 - 280) + p (1-p)^4 (528 - 280) for p