A stone is dropped into a pond. Waves in the form of circles are generated and radius of outermost ripple increases at the rate of $5 \mathrm{~cm} / \mathrm{sec}$. Then area increased after 2 seconds is ............

The equation of normal to the curve $y=\log _\theta x$ at the point $P(1,0)$ is ............

If $f(x)=3 x^3-9 x^2-27 x+15$, then the maximum value of $f(x)$ is ...........