Pepper plants watered lightly every day for a month show an average growth of 27 centimeters with a standard deviation of 8.3 centimeters, while pepper plants watered heavily once a week for a month show an average growth of 29 centimeters with a standard deviation of 7.9 centimeters. in a simple random sample of 60 plants, half of which are given each of the watering treatments, what is the probability that the difference in average growth between the two halves is between –3 an +3 centimeters?