A study indicates that 18- to 24- year olds spend a mean of 115 minutes watching video on their smartphones per month. Assume that the amount of time watching video on a smartphone per month is normally distributed and that the standard deviation is 20 minutes. Complete parts (a) through (d) below. a. What is the probability that an 18- to 24-year-old spends less than 80 minutes watching video on his or her smartphone per month? The probability that an 18- to 24-year-old spends less than 80 minutes watching video on his or her smartphone per month is (Round to four decimal places as needed.) b. What is the probability that an 18- to 24-year-old spends between 80 and 155 minutes watching video on his or her smartphone per month? The probability that an 18- to 24-year-old spends between 80 and 155 minutes watching video on his or her smartphone per month is (Round to four decimal places as needed.) c. What is the probability that an 18- to 24-year-old spends more than 155 minutes watching video on his or her smartphone per month? The probability that an 18- to 24-year-old spends more than 155 minutes watching video on his or her smartphone per month is (Round to four decimal places as needed.) d. One percent of all 18- to 24-year-olds will spend less than how many minutes watching video on his or her smartphone per month? One percent of all 18- to 24-year-olds will spend less than minutes watching video on his or her smartphone per month. Enter your answer in each of the answer boxes.