A researcher wants to know the effect of four different types of fertilizers on the mean number of tomatoes produced. He wants to estimate the treatment means μ1, μ2, μ3, and μ4 such that he will be 90% confident that the estimates are within five tomatoes of the true mean number of tomatoes. What is the necessary number of replications to achieve this goal? It is known from previous experiments that the numbers of tomatoes per plant have ranged from 20 to 60.