Units and Measurements Questions

In an experiment, the percentage of error occurred in the measurement of physical quantities $A,B,C$ and $D$ are $1\%,2\%,3\%$ and $4\%$ respectively. Then the maximum percentage of error in the measurement $X$, where $X=\frac{A^2{B}^{1/2}}{C^{1/3}{D}^3}$, will be:

The main scale of a vernier calliper has $n$ divisions/cm. $n$ divisions of the vernier scale coincide with $(n-1)$ divisions of the main scale. The least count of the vernier calliper is: