[3] 7. When a drop of milk powder is added to some coffee: Brownian motion causes the powder to gradually dissipate and mix evenly into the coffee. Suppose the concentration of milk powder at the point where the drop enters the cup follows the differential equation d0 (it : kC(t) and that the initial concentration is 10 g/L, the concentration after 1 second is 6 g/ L. ['2] (a) Find CG) and assign an exact value to the constant ls. [1] (b) At what. time does the concentration drop to 2 g/L