An object whose mass is $7\mathrm{.}8$ kg occupies a volume of $0\mathrm{.}7m^3.$ Determine its $($a$)$ weight, in newtons, and average density, in $k\frac{g}{m^3},$ at a location on the carth where $g=9\mathrm{.}55\frac{m}{s^2},($b$)$ weight, in newlons, and average densily, in $k\frac{g}{m^3},$ on the moon where $g=1\mathrm{.}7\frac{m}{s^2}.$