A taxi driver has an income regulated by his workplace. The amount of wage he receives is the UMR (Regional Minimum Wage) plus the product of the number of passengers and the customer satisfaction rating (index) each month. The customer satisfaction index in a given month is less than the number of passengers during that month. The taxi driver's service price is denoted as , the number of passengers is denoted as , and the customer satisfaction index is . The UMR in the place where the driver lives is .
If in a month a driver gets passengers, then his income is....