In the following circuit, what are the values of $P$ and $Q$?

The circuit diagram shows a logic combination. Initially, for inputs $P, Q, R$ and $S$ all at state $1$, the outputs are $X=1, Y=1$ and $Z=0$. When inputs $P$ and $R$ change to state $0$ while inputs $Q$ and $S$ remain at state $1$, what are the new states of outputs $X, Y$ and $Z$?

In the given digital circuit,if the inputs are $A=1, B=1$ and $C=1$,then the values of $y_1$ and $y_2$ are respectively:

The following configuration of gates is equivalent to

The resultant logic gate from the combination of the following gates is:

To get an output $1$ from the circuit shown in the figure,the input must be