7. A priority encoder circuit has four inputs, X3, X2, Xx1, xo. The circuit has three outputs, z, y, yo. If one of the inputs is 1, z is 1 and y, and yo represent a 2-bit, binary number whose value equals the index of the highest numbered input that is 1. For example, if x2 is 1 and x3 is 0, then the outputs are z=1 and y = 1 and yo = 0. If all inputs are 0, z = 0 and y, and yo are don't-cares. Build the truth table of the function. (3 points)