There are three Taps $\mathrm{A}, \mathrm{B}$ and $\mathrm{C}$in a tank. They can fill the tank in $10 \mathrm{hrs}, 20 \mathrm{hrs}$ and $25 \mathrm{hrs}$ respectively. At first, all of them are opened simultaneously. Then after $2 \mathrm{hours}$, tap $\mathrm{C}$is closed and $\mathrm{A}$and $\mathrm{B}$are kept running. After the $4th$hour, tap $\mathrm{B}$is also closed. The remaining work is done by Tap $\mathrm{A}$alone. Find the percentage of the work done by Tap $\mathrm{A}$by itself.