Please solve it.

According to a survey, freshman students can't stand Stat class. The amount of time he/she can sit in stat class before storming out follows an exponential random variable, with rate 0.024. Given that Rose (a freshman student) has already been sitting in Stat class for 10 minutes, what is the probability she will stay sitting in the classroom for more than 20 minutes? 0.136 0.787 20.274 0.658 0.473