Explanation:

To solve the problem, let's calculate the required marked price.

- Radha wants to earn a profit of 25% on the cost price of Rs 1680.

- Therefore, the selling price (SP) should be:

$$ SP = 1680 + (0.25 \times 1680) = 1680 + 420 = ?2100 $$

- The selling price is after a 16% discount on the marked price (MP).

- This means:

$$ SP = MP \times (1 - 0.16) = MP \times 0.84 $$

$$ 2100 = MP \times 0.84 $$

$$ MP = \frac{2100}{0.84} = ?2500 $$

- Option:1 ?2800 - This is too high.

- Option:2 ?2000 - This is too low.

- Option:3 ?2100 - This represents the selling price, not the marked price.

- Option:4 ?2500 - This is the correct marked price.