Errors and Approximations

Given $f\left(x\right)=x^3-4x$, if $x$ changes from $2$ to $1.99$, then the approximate change in the value of $f\left(x\right)$ is

If the radius of a sphere is measured as $9 \mathrm{cm}$ with an error of $0.03 \mathrm{cm}$, then find the approximate error in calculating its surface area.

If the error committed in measuring the radius of the circle is $0.05\%$, then the corresponding error in calculating the area is