$42.$ A pontoon is to be built with gasoline drums of $0\mathrm{.}5$ m diameter in the vertical axes. The drums have their axes spaced $1\mathrm{.}8$ m along each edge of the bridge and dip $0\mathrm{.}75$ m when the bridge is loaded. What distance s is required for a metacentric height of $0\mathrm{.}9$ m$,$ when GG $=1\mathrm{.}2$ m$?$ G represents the center of gravity of the body and G its center of gravity.