For earthquakes with a magnitude 7.5 or greater on the Richter​ scale, the time between successive earthquakes has a mean of 498

days and a standard deviation of 360

days. Suppose that you observe a sample of four times between successive earthquakes that have a magnitude of 7.5 or greater on the Richter scale.
a. On​ average, what would you expect to be the mean of the four​ times?