A survey among freshman at a certain university revealed that the time spent studying the week before final exams was normally distributed with a mean of 25 hours and a standard deviation of 7 hours. What proportion of freshman students study less than 30 hours the week before final exams?

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?