Answer
$2.55\;s$
Work Step by Step
The distance between the Earth and the Moon is: $ d= 3.82\times10^8\;m$
Therefore, the predicted value of the time for the laser to travel from an Earth-bound observatory to a reflector on the Moon is
$t=\frac{2d}{c}$
or, $t=\frac{2\times(3.82\times10^8)}{3\times10^8}\;s$
or, $t=2.55\;s$
