(1). Two pipes can fill a tank in 5 hours and 20 hours respectively. The pipes are opened simultaneously and the tank was not filled on time due to leak at the bottom of the tank, it took 2 hours more to fill the tank. Working alone how long will the leak take to empty the full tank?

• (a). 8 hours
• (b). 12 hours
• (c). 15 hours
• (d). 20 hours
• (e). None of these