For $2*1$ multiplexer, output equation is : $Y=S’I_0+SI_1$
So output of first multiplexer $(f_1):\bar1*0+1*1=1$
Now output of $f_1$ will send to as input for multiplexer $f_2$
So output of second multiplexer $(f_2):\bar0*P+0*1 \implies1*P=P$
Now $f_2$ will send as input to $F$,so output is: $F=\bar1*Q+1*P\implies 0*Q+P\implies P$
So final output is $F=P.$