The mean weight of a box of cereal filled by a machine is16.0ounces, with a standard deviation of0.5ounce. 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.)

a) less than 15.6 ounces

b) between 15.7 and 16.3 ounces