What Is the Formula for Calculating Mean Arterial Pressure (MAP)

What is the formula for calculating mean arterial pressure (MAP) ?

A) Averaging three of the patient's blood pressure readings over a 6-hour period
B) Dividing the systolic pressure by the diastolic pressure
C) Adding the systolic pressure and two diastolic pressures and then dividing by 3
D) Dividing the diastolic pressure by the pulse pressure