Need help with effusion question!?

Question

2.014×10-4 mol of an unidentified gaseous substance effuses through a tiny hole in 79.8 s.
Under identical conditions, 1.960×10-4 mol of argon gas takes 89.5 s to effuse.
What is the molar mass of the unidentified substance (in g/mol)?

----

HELP plz!!

Answer 1

Molar mass of Argon = 40

So, M/40 = (1.960/89.5)^2 / (2.014/79.8)^2

So, M = 30.11

Thus the gas' molar mass is 30.11