So I can simply take out (x_a) and (x_b) right? and the answers to the four senarios would be:In all of these equations, are (x_a) and (x_b) Boolean values (i.e., either a 0 or a 1)?

When (x_a) is to Vref and (x_b) to ground: Vut = (3/4)*Vref

When (x_a) is to ground and (x_b) to Vref: Vut = (1/2)*Vref

When both (x_a) and (x_b) are to Vref: Vut = (3/4)*Vref

When both (x_a) and (x_b) are to ground: Vut=0

Or are my calculations wrong?