The weights of ripe watermelons grown at Mr. Smith's farm are normally distributed with a standard deviation of 2.8 lb. Find the mean weight of Mr. Smith's ripe watermelon is only 6% weigh more than 15lb. Once the mean is known, find the probability that a watermelon from his farm weighs less than 13 lb. Please help me figure out these answers, most importantly how to do the problems.