There are two common systems for measuring temperature, Celsius and Fahrenheit. Water freezes at $0^{\circ}$ Celsius $\left(0^{\circ} \mathrm{C}\right)$ and $32^{\circ}$ Fahrenheit $\left(32^{\circ} \mathrm{F}\right) ;$ it boils at $100^{\circ} \mathrm{C}$ and $212^{\circ} \mathrm{F}$.
(a) Assuming that the Celsius temperature $T_{C}$ and the Fahrenheit temperature $T_{F}$ are related by a linear equation, find the equation.
(b) What is the slope of the line relating $T_{F}$ and $T_{C}$ if $T_{F}$ is plotted on the horizontal axis?
(c) At what temperature is the Fahrenheit reading equal to the Celsius reading?
(d) Normal body temperature is $98.6^{\circ} \mathrm{F}$. What is it in $^{\circ} \mathrm{C} ?$