According to a study by Dr ,John McDougall of his live-in weight loss program at St. Helena hospital, the people who follow his program lose between six and 15 pounds a month until they approach trim body weight. Let's suppose that the weight loss is uniformly distributed. We are interested in the wright loss of a randomly selected individual following the program for one month.

-Suppose it is known that the individual lost more than 9 pounds in a month. Find the probability that he lost less than 13 pounds in the month.