Please explain this properly

An expensive watch is powered by a 3-volt lithium battery expected to last five years. Suppose the life of the battery has a standard deviation of 0.3 year and is normally distributed. a. Determine the probability that the watch's battery will last longer than 5.5 years. b. Calculate the probability that the watch's battery will last more than 4.75 years. c. Compute the length-of-life value for which 20% of the watch's batteries last longer. a. The probability that the battery will last longer than 5.5 years is (Round to four decimal places as needed.) b. The probability that the battery will last more than 4.75 years is (Round to four decimal places as needed.) c. The length-of-life value for which 20% of the batteries last longer is years. (Round to one decimal place as needed.)