Suppose You Are Interested in Explaining Variation in Mile Run

Suppose you are interested in explaining variation in Mile Run Time in a sample of 22,359 individuals over the age of 18 and that you estimate the sample regression function (standard errors in parentheses)

$\begin{array}{lllll} \text {Mile Run Time} _ { i } =& 7.28 +& 0.09 \text {Weight} _ { i } +& 0.13 \text {Age} _ { i } -& 0.43 \text {Days Exercise per Week } _ { i }\\ \\&(2.36) &(0.04)&(0.06)&( 0.13 )\\\end{array}$

a)Which variable do you suspect could be responsible for heteroskedasticity in this model? Why? Explain.
b)How would you use the modified White's test to determine whether heteroskedasticity is present? Explain.
c)What would be your most preferred method for correcting for the potential heteroskedasticity? Explain.