power supply in Nigeria is assumed to be normally distributed with daily mean at 68 minutes and variance 49 minutes .what is the probability of having power supply for

(1) less than 45 minutes?
(2) at least 1 hour?
(3) between 75 minutes and 90 minutes?

variance of 49 minutes ----> SD = 7

find the z-score for 45 minutes, 60 minute, 75 min and 90 min , as you will need them

notice the z-score for 45 minutes
= (45-68)/7 = -3.2857

most tables or charts will give you results for z-scores between -2.99 and +2.99
values outside that range is statistically 0%

The other parts are routine questions that you should be able to do if you study this topic.