And that's exactly what it is: a RF Power Combiner simply combines (sum) different signals in a single output. In the above case, the signals are transmitted over port B and C go out through that output (A).
The body mass index (BMI) or Quetelet index is a value derived from the mass (weight) and height of an individual. The BMI is defined as the body mass divided by the square of the body height, and is universally expressed in units of kg/m 2, resulting from mass in kilograms and height in metres.
BMI = Weight in Kg / Height in Meters Squared. or alternatively, BMI = Weight in Pounds x 703 / Height in Inches Squared. So a first step to see how much you should weigh is to calculate your BMI, look at your weight category and then aim for your BMI to be in the normal weight range.