A component can be produced by any of the four processes $I$, $II$, $III$ and $IV$. The fixed cost and the variable cost for each of the processes are listed below. The most economical process for producing a batch of $100$ pieces is

$$\begin{array}{|c|c|c|} \hline \textbf{Process} & \textbf{Fixed cost (in Rs.)} & \textbf{Variable cost per piece (in Rs.)} \\ \hline I & 20 & 3 \\ \hline II & 50 & 1 \\ \hline III & 40 & 2 \\ \hline IV & 10 & 4 \\ \hline \end{array}$$

- $I$
- $II$
- $III$
- $IV$