3. Provide a design of the sequential circuit for the vending machine controller: One product sells for $0.40, and the machine takes only quarters (input Q) and dimes (input D) with an output signal I for product release and a few necessary output signals for change release (if there is change to return), for example, C5 for a 5-cent change, C10 for a 10-cent change, etc.. No other signals are used.

(a) Show the complete state diagram and state transition table.

(b) How many flip-flops are needed? Draw a block diagram of the circuit showing the key blocks, signals and wires.

(c) How many K-maps are needed to derive the complete circuit?