Oscar T. Grady is the production manager for Citrus Groves Inc., located just north of Ocala, Florida. Oscar is concerned that the last 3 years' late freezes have damaged the 2,500 orange trees that Citrus Groves owns. In order to determine the extent of damage to the trees, Oscar has sampled the number of oranges produced per tree for 42 trees and found that the average production was 525 oranges per tree and the standard deviation was 30 oranges per tree. (a) Estimate the population standard deviation from the sample standard deviation. (b) Estimate the standard error of the mean for this fi nite population. (c) Construct a 98 percent confi dence interval for the mean per-tree output of all 2,500 trees. (d) If the mean orange output per tree was 600 oranges 5 years ago, what can Oscar say about the possible existence of damage now?