During a calender year, the average electricity cost to run air-conditioning in an office is $775, with a standard deviation of $145 Assume the distribution of electricity costs for offices is bell-shaped. a) What is the probability of one office having an air conditioning electricity cost less than $800, for a calender year? b) Now, if random sample of 40 offices was selected, what is the probability that th e average air conditioning electricity cost, for this sample, is less than $800, for a calender year? Briefly explain the differences in your answers to part a) and part b d) Now, you are told that the population standard deviation is not known: What is the value of the population standard deviation, if the population mean