Step 1: Understanding the Approach:
Instead of recalculating the whole profit and loss twice, we can track just the change caused by the extra sales, since the fixed cost and the loan interest never move.
Step 2: Key Formula:
Each extra unit sold adds its full selling price minus its variable cost to profit before interest and tax (EBIT), because fixed cost is already covered by the original volume. So the rise in EBIT equals the rise in contribution, and fixed cost cancels out of the change.
Step 3: Detailed Working:
Contribution per unit $= 200 - 100 = Rs. 100$.
At the original volume of $100000$ units, contribution $= 100000 \times 100 = Rs. 1,00,00,000$, and EBIT $= 1,00,00,000 - 40,00,000 = Rs. 60,00,000$.
A $20\%$ jump in sales adds $20000$ extra units, worth $20000 \times 100 = Rs. 20,00,000$ of extra contribution. Since fixed cost stays put, EBIT simply rises by this same Rs. $20,00,000$, from Rs. $60,00,000$ to Rs. $80,00,000$.
The loan interest of Rs. $2,00,000$ a year is fixed too, so profit before tax rises from $60,00,000 - 2,00,000 = Rs. 58,00,000$ to $80,00,000 - 2,00,000 = Rs. 78,00,000$, a rise of exactly Rs. $20,00,000$, since the fixed interest cancels out of the difference.
Tax is charged at a flat $30\%$ on profit before tax in both years, so the $(1-0.30)$ factor sits on both the original and the new figure and cancels out when we take a percentage change. This means the percentage change in profit after tax is the same as the percentage change in profit before tax.
Step 4: Final Answer:
Percent change $= \dfrac{20,00,000}{58,00,000} \times 100 \approx 34.5\%$.
So KK's earnings rise by about $34.5\%$, matching option E.