2. In the preceding problem, the water outflow at each instant is, say r[t] = p, where r[t] is the water outflow at time t and p > O is a constant. The problem is to find the time it takes for the concentration of pollutants in the lake to fall to 5% of its initial value if all the sources of pollution into the lake cease to exist. Now suppose that the water outflow at each instant t, namely r[t], is not constant, but varies through time around the mean p, and is given by r[t] = p (1 + E Sin[2 1T t]), where E, 0