Question

The length of time, L hours, that a phone will work before it needs charging is normally distributed with a mean of 90 hours and a standard deviation of 15 hours. Find the probability that

1. The phone will work exactly 98 hours.                                                            

2. The phone will work more than 127 hours                                                      

3. The phone will work between 75 hours and 105 hours                                   

4. The phone will work less than 75 hours or more than 120 hours.                   

Answer 1