The correct answer is A. Rs. 4,98,750.
Let $x$ be the sales revenue at 70% capacity. We know that the sales revenue at 60% capacity is Rs. 4,50,000. We also know that the selling price falls by 5%. This means that the new selling price is 0.95 times the old selling price.
We can use the following equation to find $x$:
$x = 0.7 \times 4,50,000 \times 0.95 = 4,98,750$
Therefore, the sales revenue at 70% capacity is Rs. 4,98,750.
Option B is incorrect because it is the sales revenue at 100% capacity. Option C is incorrect because it is the sales revenue at 60% capacity. Option D is incorrect because it is the sales revenue at 70% capacity with no change in selling price.