You drop a stone down a well. You hear the splash $1\mathrm{.}63$ s later. How deep is the well? The

speed of sound in air is $343$ m$/$s$.$

A$)6\mathrm{.}96$ m$$ B$)18\mathrm{.}8$ m$$ C$)20\mathrm{.}0$ m$$ D$)20\mathrm{.}2$ m$$ E$)12\mathrm{.}5$ m