All right, part C. At what time t, where t, where zero is less than or equal to t is less than or equal to eight, is the amount of water in the pipe at a minimum? Justify your answer. All right, well let's define a function w that represents the amount of water in the pipe at any time t, and then we can figure out how to figure out the minimum value for w over that interval. So let's just say w of t, so that's the amount of water in the pipe at any given time t, it's going to be equal to, well we start with 30 cubic feet of water in the pipe at t equals zero, they tell us that right up here. So we start with that much, and then we are going to add or take away some amount. So then it's going to be plus, we're going to sum up from time zero to time t, remember this is a function of t. Well let's sum up our net inflow times little small changes in time, and we'll sum up all those small changes in time from zero to t, and that'll give us our aggregate inflow, our aggregate net inflow. So what is our net inflow?