Step 1: Understanding the Concept:
This question requires the application of the relationship between Average Revenue (AR), Marginal Revenue (MR), and the price elasticity of demand (\(e\)). Average Revenue is the same as the price of the good (\(AR = P\)).
Step 2: Key Formula or Approach:
The relationship between MR, AR, and elasticity of demand is given by the formula:
\[ MR = AR \left( 1 - \frac{1}{e} \right) \]
where \(e\) is the price elasticity of demand.
Step 3: Detailed Explanation:
We are given the following values:
\begin{itemize}
\item Price elasticity of demand, \(e = 3\).
\item Average Revenue, \(AR = \text{Rs. } 30\).
\end{itemize}
Substitute these values into the formula:
\[ MR = 30 \left( 1 - \frac{1}{3} \right) \]
First, solve the expression inside the parenthesis:
\[ 1 - \frac{1}{3} = \frac{3}{3} - \frac{1}{3} = \frac{2}{3} \]
Now, multiply this by the Average Revenue:
\[ MR = 30 \times \frac{2}{3} \]
\[ MR = \frac{60}{3} = 20 \]
Thus, the Marginal Revenue will be Rs. 20.
Step 4: Final Answer:
The Marginal Revenue will be Rs. 20.