Not sure what to do please help.

A liquid mixture containing 10.0wt%n-octane and the balance n-decane flows into a tank mounte on a balance. The mass in kg indicated by the scale is plotted against time. That data fall on a straight line that passes through the points (t=3.00min,m=145kg) and (t =12.00,m=231kg) Estimate the volumetric flow rate of the liquid mixture. L/min What does the empty tank weigh