So the pipe will begin to overflow when it crosses 50 cubic feet of water. You could say right when it hits 50 cubic feet of water, then it will begin to overflow. So we can figure out at what time does the pipe have 50 cubic feet of water in it. And so we could just say, well, w of this time, so I used uppercase w as my function for how much water is in the pipe, so capital w of lowercase w is going to be equal to 50. And so you would just solve for the w. And they say write, but do not solve, an equation. Well, just to make this a little bit clearer, if uppercase w of lowercase w is going to be 30 plus the integral from 0 to w, and actually now since I don't have t as one of my bounds, I could just say r of t minus d of t dt, so let me just do that. r of t minus d of t dt, so this is the amount of total water in the pipe at time w. Well, this is going to be equal to 50.