Iterate over matrix?

In the attached MathCAD 3.1 worksheet and screenshot I'm attempting to determine the left reaction force for three beams of the same length with different loadings. The equation works for one beam but I'd like it to work for all 3 (or more). Each row of the pp matrix gives the 2 loads on each of the 3 beams. The y vector gives the load application point on each beam (it's the same for each beam).

My question is, how do I iterate the equation for R over the three beams such that the resultant is a [3x1] vector giving the R (reaction) for each beam?