**The correct option is (A) 40.**

Let the leak empties the full tank in x h then

Part emptied in 1 h by leak = \(\frac{1}{x}\)

Part filled by inlet in 1 h = \(\frac{1}{20}\)

**According to the question.**

**[Negative sign indicates emptying]**

Clearly, leak will empty the full tank in 40 h.