When there's a big difference, you expect a steeper rate of change, but then when there's less of a difference, the rate of change, you can imagine, becomes less and less and less negative as we asymptote towards the ambient temperature. So with this out of the way, now let's tackle part A. Write an equation for the line tangent to the graph of h at t equals zero. Use this equation to approximate the internal temperature of the potato at time t equals three. So what are we going to do? Well, we're going to think about what's going on at time t equals zero, right over here. We want the equation of the tangent line, which might look something like this, at t equals zero.