#two-sample-test

Plots of farmland yield on average 1,215 lb of corn with a standard deviation of 94 lb per plot. An experiment will give each plot either the current or a new fertilizer, with equal numbers of plots per fertilizer. How many plots per fertilizer are needed to detect a difference of 40 lb per plot with 90% power, using a two-sided test at $\alpha = 0.05$? Use normal quantiles rounded to two decimals, and round the number of plots up.