Answer
BSA increases more rapidly at lower body mass
Work Step by Step
$f(m)$ = $\frac{\sqrt {hm}}{60}$
replace $h$ = $180$
$f(m)$ = $\frac{\sqrt m}{\sqrt 20}$
$f'(m)$ = $\frac{1}{2\sqrt {20m}}$
$m$ = $70$ $kg$
$f'(70)$ = $\frac{1}{2\sqrt {20\times70}}$ = $0.0134$ $m^{2}/kg$
$m$ = $80$ $kg$
$f'(80)$ = $\frac{1}{2\sqrt {20\times80}}$ = $0.0125$ $m^{2}/kg$
Because the rate of change of BSA depends on 1=pm, it is clear that BSA increases more rapidly at lower body mass
