The overall objective is to create a 4-key digital lock. The system has four digital inputs and one digital output. The LED will be initially on, signifying the door is locked. Define two separate key codes, one to lock and one to unlock the door. For example, if the keys are numbers 1, 2, 3, and 4, one possible key code is 23. This means if you push both the 2 and 3 keys (not pushing the 1, 4 keys) the door will unlock. Implement the design such that the unlock function occurs in the software of the 6811/6812.