Combination of Errors

The physical quantity $S$ is given by $S=\frac{a^2{b}^3}{c\sqrt{d}}$.

The errors of measurements in $a,b,c,d$ are $4\%,2\%,3\%,1\%$ respectively, find the percentage error in the measurement of $S$.

The measured value of mass, length, breadth and thickness of a rectangular block are $39.9 \mathrm{g}, 5.12 \mathrm{cm}, 2.56 \mathrm{cm} \mathrm{and} 0.37 \mathrm{cm}$ respectively. Find the maximum permissible percentage error in the determination of the density of the material of the block.