logic circuit

Hello everyone, I have a problem and I thought I should post it here because I can't quite get the hang of it. I was tasked to make a circuit that is made of only NOR-gates. Seemed simple at first but then the restrictions came in. The circuit needs to be made out of 4 NOR gates with 2 inputs...

How will the output of a combinational logic circuit change once the input is withdrawn? It will definitely change, how will it change?

Hello. This is JK flip-flop. I have to convert it into D flip-flop, that it does the same what JK does. Then I have to draw a logic circuit of D flip-flop. I don't know what to do, can you help me?