Hi everyone. Can you help me with the following?

There is no "equilibrium," as there is an endless oscillation. There is an ambiguity in the question as we are not told whether D-sub-t is the amount in the blood system immediately before or immediately after the administration of the drug. In the long run, though, the amount in the blood system immediately before administration of the drug will be 6 cc, and the amount immediately after administration of the drug will be 8 cc.

So if D-sub-t means the amount of the drug present in the blood system immediately before administration of the t-th dose, the limit as t-->infinity is
D0*(1-p)/p, and the answer to (b) is 6.