4.25 A professor teaches a large class and has scheduled an examination for 7:00 p.m. in a different classroom. She estimates the probabilities in the table for the number of students who will call her at home in the hour before the examination asking where the exam will be held.

Number of calls 0 1 2 3 4 5 Probability 0.10 0.15 0.19 0.26 0.19 0.11 Find the mean and standard deviation of the number of calls.