So since time is in years, that would be three months would be 1 4th of a year, so T equals 1 4th. So it seems at first it's really daunting, they gave us a differential equation, we don't even know what W, what the actual function W is, how do we figure out its tangent line, but we just have to kind of think about what they're asking. So regardless of what W looks like, so let's think about it a little bit. So we don't know yet what W actually does look like, but they tell us it's an increasing function. So at time zero, it has 1,400 tons in it, they tell us that right up here, and then it increases. We don't know what the function actually does look like, but let's say that that is W. So what they're saying in problem A, is they're saying use a tangent line to the graph at T equals zero. So there's, let me actually, let me draw W a little bit differently.