An ideal gas changes its state from $\mathrm{A} to \mathrm{C} in two different paths \mathrm{ABC} and \mathrm{AC}. The internal energy of the gas at state \mathrm{C} is 20 \mathrm{~J} and at state \mathrm{B} is 10 \mathrm{~J}. Heat supplied to the gas to go from \mathrm{B} \rightarrow \mathrm{C}$ is