When a polling company calls a telephone number at random, there is only a 9% chance that the call reaches a live person and the survey is successfully completed. Suppose the random digit dialing machine makes 15 calls. Let X = the number of calls that result in a completed survey. (a) Calculate and interpret the mean of X.

(b) Calculate and interpret the standard deviation of X​

Runners run around the school's football field. the cross country coach determines that the width of the field is seventy yards shorter than the length. part a write an expression that represents the perimeter of the football field. let x represent the length of the football field. include parentheses in your expression. next, write an equivalent expression that does not include parentheses. what property or properties did you use to simplify? explain. part b the cross country coach later determines that the length of the football field is 120 yards. all students must run five laps. using your answer from part a, determine the actual number of yards that each athlete must run in the tryouts. in order to make the team, students must complete the laps in 6 minutes. how quickly must they run each lap?