The amount of time in REM sleep can be modeled with a random variable probability density function given by F ( x ) = x 1600 where 0 ≤ x ≤ 40 Y x is measured in minutes. 1. Determine the probability that the amount of time in REM sleep is less than 7 minutes. 2. Determine the probability that the amount of time in REM sleep lasts between 13 and 24 minutes.