The undercarriage of a commercial aircraft has three positions and there is an indication for each undercarriage. First, it is retracted, doors closed and locked in position, and there is no light indication in the cockpit. In the second position, the undercarriage is down and locked; this is shown as a green light in the cockpit for each undercarriage. When a red light shows then that undercarriage is neither up or down, but most importantly it is not locked in position. Assume that, initially, the airplane is on the ground at the departure gate. Describe the lights status in all stages from start of take-off to parking at the terminal after a flight. Describe for one of the following airplanes (A320, A340 or B747). In addition, at any stage of flight (you may decide at which stage) any of the undercarriages failed to respond to the input signal from the pilot. Identify the data types of variables and constants needed to simulate the process you described. Fully justify your selections and reasoning.