In order to evaluate energy demand for heating services, the number of heating degree days are calculated. The number of heating degree days can be calculated by the formula H = 65 - T, where 65 is degrees Fahrenheit, and T is the average of the high and low temperatures for the day. If the high temperature for a day was 51°F and the low temperature for the same day was 45°F, what is the number of heating degree days?