Concept:
In agency transactions:
- Ordinary commission is calculated on total sales.
- Del-credere commission is an additional commission given to the agent for guaranteeing credit sales, and it is calculated only on credit sales.
Step 1: Calculate the ordinary commission.
Total sales = ₹50,000
\[
\text{Ordinary commission} = 5% \times 50,000
\]
\[
= \frac{5}{100}\times 50,000 = ₹2,500
\]
Step 2: Calculate the del-credere commission.
Credit sales = ₹20,000
\[
\text{Del-credere commission} = 2% \times 20,000
\]
\[
= \frac{2}{100}\times 20,000 = ₹400
\]
Step 3: Find the total earning of the agent.
\[
\text{Total earning} = \text{Ordinary commission} + \text{Del-credere commission}
\]
\[
= 2,500 + 400 = ₹2,900
\]
Step 4: Final Answer.
\[
\boxed{\text{Total earning of the agent} = ₹2,900}
\]