What is the Boolean expression for the output f of the combinational logic circuit of NOR gates given below?

The Boolean expression for the output $$f$$ of the multiplexer shown below is

Suppose the predicate $$F(x,y,t)$$ is used to represent the statements that person $$x$$ can fool person $$y$$ at time $$t$$. Which one of the statements below expresses best the meaning of the formula $$\forall x\exists y\exists t\left( {\neg F\left( {x,y,t} \right)} \right)?$$

Consider a company that assembles computers. The probability of a faulty assembly of any computer is P. The company therefore subjects each computer to a testing process. This gives the correct result for any computer with a probability of q. What is the probability of a computer being declared faulty?