Sick leave time used by employees of a firm in the course of 1 month has approximately a normal distribution with a mean of 180 hours and a variance of 350 hours.

a Find the probability that the total sick leave for next month will be less than 150 hours.  

b In planning schedules for next month, how much time should be budgeted for sick leave if that amount is to be exceeded with a probability of only 0.10?