$7\mathrm{.}2$ A $12-cm$ diameter cylindrical can is filled to a depth of $10$ cm with motor oil $(=878k\frac{g}{m^3}).$ Find the mass and weight of the motor oil.

$7\mathrm{.}3$ The fuel tank of a tuck las a capacity of ${55}^5$ gal. If the tank is full of gasoline $(sg=0\mathrm{.}751),$ what is the mass and weight of the gasoline in SI units:

$7\mathrm{.}4$ A $5-$in diameter spherical balloon contains hydrogen. If the density of the hydrogen is $=0\mathrm{.}0830k\frac{g}{m^3},$ what is the mass and weight of the hydro$-$