Correct answers:$\text {mean=}7.5\text {min}$mean=7.5min . The mean of a random variable with a uniform distribution U (a,b) is. μ=a+b2. (this is the midpoint of the interval [a,b]). So in this case, a=4 and b=11, so the mean isa+b2=4+112=152=7.5So the average waiting time is 7.5 minutes. Lexie is waiting for a train.