The ratio of effusion ratios between He(g) and SF6(g) is

rate He = 6 x rate SF₆

Graham's law: the rate of effusion of a gas is inversely proportional to the square root of its molar masses or  

the effusion rates of two gases = the square root of the inverse of their molar masses:  

or  

M He = 4 g/mol

M SF₆ = 146 g/mol

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.