(2) If $a=\frac{\ln 2}{2}, b=\frac{\ln 3}{3}, c=\frac{\ln \pi}{\pi}, d=\frac{\ln 2.72}{2.72}, f=\frac{\sqrt{10} \ln 10}{20}$,

then the order of $a, b, c, d, f$ from smallest to largest is $\qquad$
(2) $a<f<c<b<d$