An electric company charges a certain rate per kilowatt-hour (\text{kWh})(kWh)left parenthesis, start text, k, W, h, end text, right parenthesis of electricity used and an administrative fee of \$3.50$3.50dollar sign, 3, point, 50. The company charged Zhao \$63.25$63.25dollar sign, 63, point, 25 for using 800\,\text{kWh}800kWh800, start text, k, W, h, end text of electricity. Zhao uses the equation, 63.25=800r+3.5063.25=800r+3.5063, point, 25, equals, 800, r, plus, 3, point, 50 to represent the situation.
What does the variable rrr represent in the equation?