What was the difference between the average amount invested in raw materials during the given period and the average value of sales of finished goods during this period?

Answer: Option D

Average of total investment
  $$=\frac{1}{6}$$ (120 + 225 + 375 + 330 + 525 + 420)
$$\begin{array}{rl}& =\frac{1}{6}\times 1995\\ & =\text{Rs. }332.5\text{ lakhs}\\ & \text{Average of sales}\end{array}$$
  $$=\frac{200+300+500+400+600+460}{6}$$
$$\begin{array}{rl}& =\frac{2460}{6}\\ & =\text{Rs. }410\\ & \text{Difference}=410-332.5\\ & =77.5\text{ lakhs}\end{array}$$