During a year, Mark's monthiy sales compensation ranged between $12,500 and $16,700 per month and units sold ranged between 1,000 and 1,800 units for those same months. Required: Use the high-low method to determine Mark's monthly salary and commission rate per unit sold and then calculate the total number of units sold in a year when Mark's total compensation amounted to $139,500 (Round your "Commission rate" to 2 decimal places.) Monthly salary Commission rate per unit Total number of units sold