The probability model below describes the number of repair calls that an appliance repair shop may receive during an hour. Complete parts a and b below. Repair Calls Probability 1 2 3 4 0.2 0.4 0.2 0.2 a) How many calls should the shop expect per hour? The shop should expect calls per hour. (Type an integer or a decimal. Do not round.) b) What is the standard deviation? The standard deviation is . (Round to two decimal places as needed.)