Suppose that the lifetimes of light bulbs are approximately normally​ distributed, with a mean of 57 hours and a standard deviation of 3.5 hours. With this​ information, answer the following questions.
​(a) What proportion of light bulbs will last more than 61 ​hours?
​(b) What proportion of light bulbs will last 52 hours or​ less?
​(c) What proportion of light bulbs will last between 59 and 62 ​hours?
​(d) What is the probability that a randomly selected light bulb lasts less than 45 ​hours?