[填空题]
A hiker determines the length 0 arr).wbu-gk of a l. xkp jw f91q-rmo3pa*ake by listening for the echo of her shout reflected by a cliff at the far enqm.9w-rkp a p13*fo xjd of the lake. She hears the echo 2.0 s after shouting. Estimate the length of the lake. $\approx$ $ \times10^{ 2}$m
