In the Kjeldahl method, the nitrogen in $0.700\ \text{g}$ of a food is changed to ammonia, which is passed into $50.0\ \text{mL}$ of $0.100\ \text{mol L}^{-1}$ sulfuric acid. The acid that is not neutralised needs $20.0\ \text{mL}$ of $0.100\ \text{mol L}^{-1}$ NaOH for complete neutralisation. What is the percentage of nitrogen in the food by mass? Atomic masses in $\text{g mol}^{-1}$: H 1.0, N 14.0, S 32.0.