A drug is administered intravenously at a constant rate of 7 mg hour and is excreted at a rate proportional to the quantity present with constant of proportionality k 0 a Set up a differential equation for the quantity Q in milligrams of the drug in the body at time t hours Your answer will contain the unknown constants r and k Q 0 b Solve this differential equation assuming there is no drug in the body initially Your answer will contain r and k Q c What is the limiting long run value of Q OG 1