1 is CORRECT. F1 may be expressed as F1 = PRD M(0,3,5) therefore
          F1 * F2 = PRD M(0,3,5) * PRD M(3,5,6) 
                  = M0*M3*M5*M3*M5*M6 
                  = M0*M3*M5*M6              (recall: x*x = x) 
                  = PRD M(0,3,5,6)