A binary-to-BCD encoder has four inputs D0 C0, B0, and A0 and five outputs D, C, B, A, and VALID. The outputs D, C, B and A give the proper BCD value of the input and the VALID output is 1 if the input combination is a valid decimal code. If the input combination is an invalid decimal code, the VLID output becomes 0, and all of the D, C, B, and A outputs show 0 values. If only NOT gates and 2-input OR and AND gates are available, the minimum number of gates required to implement the above circuit is

A binary-to-BCD encoder has four inputs D0 C0, B0, and A0 and five out

1.	A binary-to-BCD encoder has four inputs D0 C0, B0, and A0 and five outputs D, C, B, A, and VALID. The outputs D, C, B and A give the proper BCD value of the input and the VALID output is 1 if the input combination is a valid decimal code. If the input combination is an invalid decimal code, the VLID output becomes 0, and all of the D, C, B, and A outputs show 0 values. If only NOT gates and 2-input OR and AND gates are available, the minimum number of gates required to implement the above circuit is
A.	10
B.	9
C.	8
D.	7
Answer» D. 7