Fire Flow Test in Javascript

calculateRatedCapacity.js

function calculateRatedCapacity(staticPressure, residualPressure, outletDiameter, pitotReading) {

  var outletCoefficient = 0.9;
  var MULTIPLIER = 29.83;
  var EXPONENT = 0.54;

  if (outletDiameter > 2.5) {
    outletCoefficient = 0.75;
  }
  var pressureToSubtract;
  if (staticPressure >= 40) {
    pressureToSubtract = 20;
  }
  if (staticPressure < 40) {
    pressureToSubtract = staticPressure / 2;
  }
  var totalTestFlow = MULTIPLIER * outletCoefficient * Math.pow(outletDiameter, 2) * Math.sqrt(pitotReading);

  var ratedCapacity = Math.pow(
	      (staticPressure - pressureToSubtract) /
				(staticPressure - residualPressure),
      EXPONENT) * totalTestFlow;

  return ratedCapacity;

}