Suppose that based upon this experiment, the scientist wishes to be 80% sure of detecting a difference of about 0.45 kg/plot in the average yield among the four nematocides when testing at =0.05. She decides to use 0.15 as an estimate of the population variance. Then: (a) The required sample size is about 20 plots per nematocide for a total of 80 plots. (b) The required total sample size is 20 plots, i.e., 5 plots per nematocide. (c) The required sample size is about 4 plots per nematocide for a total of 16 plots. (d) The required total sample size is 4 plots, i.e., 1 plot per nematocide. (e) The required sample size cannot be determined because the individual population means are not known.