1. At time \( t=0 \), a boiled potato is taken from a pot on a stove and left to cool in a kitchen. The internal temperature of the potato is 91 degrees Celsius \( \left({ }^{\circ} \mathrm{C}\right) \) at time \( t=0 \), and the internal temperature of the potato is greater than \( 27^{\circ} \mathrm{C} \) for all times \( t>0 \). The internal temperature of the potato at time \( t \) minutes can be modeled by the function \( H \) that satisfies the differential equation \( \frac{d H}{d t}=-\frac{1}{4}(H-27) \), where \( H(t) \) is measured in degrees Celsius and \( H(0)=91 \).
(a) Write an equation for the line tangent to the graph of \( H \) at \( t=0 \). Use this equation to approximate the internal temperature of the potato at time \( t=3 \).
(b) Use \( \frac{d^{2} H}{d t^{2}} \) to determine whether your answer in part (a) is an underestimate or an overestimate of the internal temperature of the potato at time \( t=3 \).
(c) For \( t<0 \), an alternate model for the internal temperature of the potato at time \( t \) minutes is the function \( G \) that satisfies the differential equation \( \frac{d G}{d t}=-(G-27)^{2 / 3} \), where \( G(t) \) is measured in degrees Celsius and \( G(0)=91 \). Find an expression for \( G(t) \). Based on this model, what is the internal temperature of the potato at time \( t=3 \) ?