P = X + Y^2 + Z^3 + W^4, where

X_1, X_2, .., X_400Y_1, Y_2, .., Y_400Z_1, Z_2, .., Z_400W_1, W_2, .., W_400

are samples from Uniform(0,1) distribution. Find 90% confidence interval for the variance of P. Note: Use at least fifty thousand simulated samples to generate sampling distr. for the variance of P.