Beyer's sells winter coats, with most of the sales being made in the months of October, November, and December. Beyer's makes a one-time purchase of coats in September at a

cost of $40 each and sells each coat for $70. Any coats unsold at the end of December are marked down to $30 and sold in a special New Year's clearance sale. Any unsold coats always sell during the clearance sale. The following is the number of sales of coats for the past 10 years: 80, 100, 80, 110, 60, 90, 80, 80, 70, 90.Estimate the mean demand for winter coats.