Salim used 3 taps to fill an empty rectangular tank with water.If only 1 tap was used,Tap A could fill the empty tank in 3 hours, Tap B could fill it in 4 hours and Tap C could fill the tank in 8 hours.

Salim first turned on Tap B for 10 minutes.then he turned on Tap A and C. One hour later, he turned off all the 3 taps. What fraction of the tank was still empty?