Running the code of the first post with the constraint I suggested in my last reply gives me:
ERROR: LoadError: BoundsError: attempt to access 8-element Array{Int64,1} at index [9, 1]
That comes from the fact that Q is a 1D array of 8 elements, and therefore sum(Q[a,w]*x[a,t] for a in A) will not work, Q needs to be a 2D array (a matrix) of 79x? where ? is at least 1 (but essentially goes up to any value w can assume). The same problem exists with WH that is also a 1D array of 8 elements but is indexed like WH[w,t] for a in A (remembering that t is 18). Replacing both Q and WH by Q = ones(79, 1); WH = ones(1, 18) makes the code execute with no error (but, obviously, probably with the wrong result).
The error message you are giving me say that you tried to index some array with a floating point. I cannot reproduce it with the code you posted here.