I do not understand how to calculate this question.

A survey Found that people keep their televisions an average of 5.4 years. The standard deviation is 0.74 year. If a person decides to buy a new TV, nd the probability that he or she owned the old one for the given amount of time. Assume the random variable is normally distributed. Refer to the table of values (9 Area Under the Standard Normal Distribution) as needed. If necessary, round intermediate calculations to the nearest hundredth. Part: 0 I 3 Part 1 of3 (a) More than 3.9 years The probability that a randomly selected person has owned his or her old TV for more than 3.9 years is D%. @)