Given a four bit binary inpu ABCD, design a circuit to give an out put of 1 if the input is valid BCD code, and a 0 otherwise.

3.a. Given a four bit binary input ABCD, design a circuit to give an output of " 1 " if the input is a valid BCD code, and a " 0 " otherwise. Realize the function using an 81 multiplexer and the minimum number of additional logic gates. 3.b. Using A and B on the control lines, realize the same function using a 41 multiplexer and the minimum number of additional logic gates. 3.c If you used C and D on the control lines instead of A and B, would your circuit be more or less minimal? Justify your