According to www.mynewplace.com, in January 2011 the average monthly rental rate for one bedroom apartments in Ann Arbor, Michigan, was $796. (Background information from www.mynewplace.com/city/ann_arbor_apartments_for_rent_michigan.) Suppose rental rates across all one-bedroom apartments in Ann Arbor follow approximately a normal distribution, with a standard deviation of $150. Using a table, calculator, or software that can provide normal probabilities, find the approximate proportion of one-bedroom apartments for which the rental rate:
a. Is at least $1000 a month.
b. Is less than $500 a month?
c. Is between $500 and $1000 a month.