The meaning of the horizontal asymptote is that the increase in a person's body temperature is a constant value when long time passes.
You can obtain that value by calculating the limit of the function when t → ∞:
4t
T(t) = ------------- => Lim T(t) when t → +∞ = 0.
t^2 + 1
That means that at long term the Temperature tends to remain at 98.6°F.
B- i could be wrong though
A = LW
A = 2/3 * 3/4
A = 6/12 = 1/2 miles^2