$$

$,$

Direct horizontal distance between sound source and receiver is $50$ meters and vertical distance between

source and solid surface is $32\mathrm{.}5$ meters, in terms of time and distance you are asked to determine

whether there is an echo or not if space is at room temperature.

$x_d=,m.$

$x_r=,m.$

$t_d=,$msec

$tr=,msec$

Enter $0$ if there is no echo

Enter $1$ if there is echo

Is there an echo?