Chapter 1.1, Problem 2P

Blood plasma is stored at ${40}^{\circ }F$. Before it can be used, it must be at ${90}^{\circ }F$. When the plasma is placed an oven at ${120}^{\circ }F$, it takes $45$ minutes to warm to ${90}^{\circ }F$. Assume that Newton’s law of cooling applies. How long will it take the plasma to warm ${90}^{\circ }F$ if the oven temperature is set at ${100}^{\circ }F$?