4. (20 points) (Lee Special Crew) The residents of Lee city deposit their refuse on the curbside at the start of each working day. The amount of refuse placed at curbside at the start of each day is an uncertain quantity whose probability distribution is given below The quantities of refuse produced on different days are all independent of one another. Refuse is collected by crews. Each crew can collect 5 tons of refuse per eight-hour working day. Each crew consists of two members, and each member receives $20 /hour (\$160/day). Whatever refuse remains at the end of the work day must be collected that evening by a special crew, who picks up the surplus at a price of $175/ ton. Determine the number of regular crews that minimizes the expected cost of garbage collection and the associated expected cost of garbage collection