The overall objective is to create an 8-key digital lock. The system has eight digital inputs and one digital output. The LED will be initially off, signifying the door is locked. Define a key sequence to unlock the door. For example, if the keys are numbers 1, 2, . . . and 8, one possible key code is 556. This means if you push the 5, release the 5, push the 5, release the 5 and push the 6, then the door will unlock. The unlock operation will be a two-second pulse on the LED.