A carpenter needs to make a wooden cuboidal box, closed from all sides, which has a square base and fixed volume. Since he is short of the paint required to paint the box on completion, he wants the surface area to be minimum.
On the basis of the above information, answer the following questions :
Find \( \frac{dS}{dx} \).
Find the interval in which $f(x) = x + \frac{1}{x}$ is always increasing, $x \neq 0$.
The logic gate equivalent to the combination of logic gates shown in the figure is