It currently costs a total of $1,000 for an automobile engine repair following a breakdown. This is based on performing oil changes every 60,000 miles. However, for every 10,000 miles an oil change is delayed, the engine repair costs following a breakdown increases by $100 (for example if the oil change is 70,000 miles, the repair cost is $1,100). Following is breakdown information for a fleet of five automobiles. The average number of breakdowns between oil changes for this fleet is as follows: