The mean weight of a box of cereal filled by a machine is 15.0 ounces, with a standard deviation of 0.5 ounce. If the weights of all the boxes filled by the machine are normally distributed, what percent of the boxes will weigh the following amounts? (Round your answers to two decimal places.) Please show your work so that I can better understand of how you came up with the answer.
(a) less than 14.7 ounces %
(b) between 14.7 and 15.3 ounces