A set of stairwell lights is controlled by the single output L of a logic circuit having inputs from three switches S2S1S0. Assume that initially all switches are DOWN and the lights are OFF. The first person to change any one of the three switches to UP turns the lights ON. The next person to subsequently alter the position of any one of the three switches turns the lights OFF. The next person turns the lights ON, etc. Determine the required logic and implement using (a) NAND gates, and (b) Exclusive-OR gates