Correct Answer - Option 3 : 20 minutes

**Given:**

All pipe together can fill the tank in 25 min

**Calculation:**

Let us assume pipe C can empty the tank in P min

⇒ One minute's work of A, B, and C together = 1/25

⇒ 1/30 + 2/75 - 1/P = 1/25

⇒ C alone can empty the tank in P = 50 minutes

⇒ C alone can empty the 2/5th tank in = 50 × (2/5) = 20 minutes

**∴ The required result will be 20 minutes.**