The following graph describes the temperature $T(t)$ of a yam in an oven, where temperature $T$ is measured in degrees Fahrenheit and time $t$ is measured in minutes:
(a) Use the graph to approximate the temperature of the yam when it is first put in the oven.
(b) Use the graph to approximate $\lim _{t \rightarrow \infty} T(t)$.
(c) What is the temperature of the oven, and why?