I would guess that the ambient room temperature is 27 degrees Celsius, and so that's why the temperature would approach this, but it would always stay a little bit greater than that as t gets larger and larger. The internal temperature of the potato at time t minutes can be modeled by the function h that satisfies the differential equation. dh dt, the derivative of our internal temperature with respect to time, is equal to negative 1 4th times r, the difference between our internal temperature and the ambient room temperature, where h of t is measured in degrees Celsius and h of zero is equal to 91. So before I even read part a, let's just make sense of what this differential equation is telling us, and let's see if it's consistent with our intuition. So let me draw some axes here. So this is my y-axis, so that is my y-axis, and this right over here is my t-axis. Now if the ambient room temperature is 27 degrees Celsius, so I'll just draw there, that's what the room temperature is doing, and so we know at t equals zero, our potato is at 91 degrees, so let's see, that's 27, 91 might be right over there.