A process at steady state has a stream entering at $500$ kg$/$hour of a mixture of $70\%$

hydrogen and $30\%$ nitrogen. Stream A exits the system at $300$ kg hydrogen$/$hour and m $1$ kg

nitrogen$/$hour; and stream B exits the system at $125$ kg nitrogen$/$hour and m$2$ kg

hydrogen$/$hour

Which of the following balances can be used to solve for the unknown masses $($m $1$ & m$2)?$

$1.$ mass balance

$2.$ mole balance

$3.$ atom balance

$4.$ volume balance

Choose the correct answer and explain your choice:

a$.1,2$

b$.1,2,3$

c$.1,3$

d$.1,2,3,4$