Computes a Priority level by combining three numbers in the range 0..1000.
The first number is a multiple of strong.
The second number is a multiple of medium.
The third number is a multiple of weak.
By convention, at least one of these numbers should be equal to or greater than 1.
Source
static double create(double a, double b, double c) {
double result = 0.0;
result += max(0.0, min(1e3, a)) * 1e6;
result += max(0.0, min(1e3, b)) * 1e3;
result += max(0.0, min(1e3, c));
return result;
}