There are students in an elementary statistics class. On the basis of years of experience, the instructor knows that the time needed to grade a randomly chosen first examination paper is a random variable with an expected value of minutes, and a standard deviation of minutes.

If grading times are independent and the instructor begins grading at 6:50 PM, and the sports report begins at 11:10 PM, what is the probability that he misses part of the report if he waits until grading is done before turning on the TV?

So

Is this correct?