In a certain experiment, magnesium boride (Mg₃B₂) reacted with acid to form a mixture of four boron (Bₓ Hу), three as liquids (labeled I, II, and III) and one as a gas (IV).
(c) Sample IV was found to be 78.14% boron. Its rate of effusion was compared to that of sulfur dioxide; under identical conditions, 350.0 mL of sample IV effused in 12.00 min and 250.0 mL of sulfur dioxide effused in 13.04 min. What is the molecular formula of sample IV?