The mass of one methane molecule is 2.7 × 10⁻²³ gram. Find the mass of 90,000 molecules of methane. Express the answer in scientific notation.
a) 2.43 × 10⁻²⁰ grams
b) 2.43 × 10⁻¹⁹ grams
c) 2.43 × 10⁻²² grams
d) None of the above.