10. The weights of envelopes sent from an insurance office are normally distributed with mean u = 11 ounces and standard deviation o = 3.5 ounces. The mail room clerk 8 would like to know the average weight of 20 envelopes. What is the probability that the mean weight x is: a. us = (round standard deviation to the nearest hundredth) b. lighter than 10 ounces? P( ) = P( c. heavier than 13 ounces? P( ) = P( d. between 10 and 13 ounces? P( ) = P(