Answer
$s_{b_1}=0.00429$
Work Step by Step
$s_e=0.368$ (item (b))
To find $s_x$:
Using the EXCEL, enter the "Commute Time" values in the column A.
Select "FORMULAS" -> "More Functions" -> "Statistical".
In A8 enter "=STDEV.S(A1:A7)"
$s_x=34.988$
$s_{b_1}=\frac{s_e}{\sqrt {∑(x_i-x ̅)^2}}=\frac{s_e}{\sqrt {n-1}s_x}$ (see note on page 684)
$s_{b_1}=\frac{0.368}{\sqrt {7-1}\times34.988}=0.00429$
