The BCD ripple counter shown in Fig. 6.10 has four flip-flops and 16 states, of which on...

The BCD ripple counter shown in Fig. 6.10 has four flip-flops and 16 states, of which only 10 are used. Analyze the circuit and determine the next state for each of the other six unused states. What will happen if a noise signal sends the circuit to one of the unused states? (HDL—see Problem 6.54.)