Problem five, at the beginning of 2010, a landfill contained 1,400 tons of solid waste. The increasing function W, so I guess W constantly increases, the increasing function W models the total amount of solid waste stored at the landfill. Planners estimate that W will satisfy the differential equation, so the derivative of W with respect to time is equal to one over 25 times the quantity W minus 300. For the next 20 years, W is measured in tons, T is measured in years from the start of 2010. All right, let's get into this. So part A, use the tangent line to the graph of W at T equals zero to approximate the amount of solid waste that the landfill contains at the end of the first three months of 2010. So since time is in years, that would be three months would be 1 4th of a year, so T equals 1 4th.