I designed my Mux gate. I know it's not the most simplified version, but still should output the desired results. I used SOP method to find the boolean equation for my chip and ended up with (a)(b)+(a)(sel)'+(b)(sel). I constructed my Mux chip accourding to this equation. However, at some point the output of Not gate is not inverted, in=1 and out=1, and this can be seen in Internal Pins window(section) of hardware simullator. I know, that correct solutions is (a)(sel)'+(b)(sel), but the above equation is also correct, just not the simplest. Please let me know if you want to examine my code.