Re-formulate changing models and interpret their results
A perfectly mixed tank initially holds 70 L with nutrient concentration 1 g/L. Inflow is 1 L/min at 3 g/L; outflow is 4 L/min at the current tank concentration. Assume no reaction, no overflow, continuous mixing and positive volume. Let M(t) be mass in grams and C=M/V. Use t=2 min for instantaneous fields. These unequal flows change the volume
\[V=V_0+\Delta t,\quad C=c_{in}+(C_0-c_{in})(V/V_0)^p,\quad M=c_{in}V+(M_0-c_{in}V_0)(V/V_0)^q\]