System and method for calculating a transmitter beamforming vector related to a channel vector h under per-antenna power constraints combined with total power constraint, under per-antenna power constraints combined with overall line of site effective isotropic radiated power and under all three constraints. Upon insertion of a payment into a payment acceptor system, a portion of oxygenated water is dispensed. Accurate and stable back pressures are maintained at total flow rates of as high as 200 ccmin.