A liquid mixture of ethanol and water is flowing as inlet stream $P$ into a stream splitter. It is split into two streams, $Q$ and $R$, as shown in the figure below.

The flowrate of $P$, containing $30$ mass$\%$ of ethanol, is $100\:kg/h$. What is the least number of additional specification$(s)$ required to determine the mass flowrates and composition (mass $\%$) of the two exit streams?

1. $0$
2. $1$
3. $2$
4. $3$