(07.01 MC) The cоncentrаtiоn оf а medicаtion M in mg/L present in the bloodstream decreases over time such that the concentration of medication is proportional to the amount of medication t hours after the first dose. The concentration of medication 30 minutes after the first dose is 80 mg/L and was decreasing at a rate of 150 mg/L per hour. Which differential equation represents this relationship?