Calculating current draw from an Amplifier

There are 2 different kinds of Amplifiers. Class D and Class AB which means there are 2 different calculations.

Class AB: Total RMS Wattage divided by 0.50 Amp Efficiency divided by 13.8 Volts equals Current Draw in Amperes.

Class D: Total RMS Wattage divided by 0.75 Amp Efficiency divided by 13.8 Volts equals Current Draw in Amperes