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**Case 3**: *r*_{1}= *r*_{2}=*r*, *k*=*k*_{1}>0, *V*=*V*_{0}

Now we have_{ }

This is separable. We get

Integrating both sides gives us

or

And thus

This gives us

To find *C*:

And thus

Finally:

We can see that case 1 is just a special case of case 3.

**An example**

Say we have *V*=*V*_{0}=2000 l, *r*_{1} = *r*_{2} = *r *= 20 l/s, *k*=*k*_{1}=10/2000 kg/l and *y*_{0} = 50 kg. This would give us the solution

This can be seen as the green curve in the figure. We can see that we asymptotically get toward the concentration of the inflow.

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