The Price King Auto Mall pays their sales staff by commission. They are paid a percent of the profit the dealership makes on each sold car. If the profit is $900 or less, the commission rate is 18%. If the profit is greater than $900 and less than or equal to $1,500, the com- mission rate is 20% of the profit. If the profit is above $1,500, the rate is 25% of the profit. If x represents the profit, express the com- mission c(x) as a piecewise function.