Help with Chemistry problem please...?

Question

When a 2.90 g sample of a non-electrolyte is dissolved in 99.83 g of water, the resulting solution freezes at -0.62 C. The Kf for water is 1.86 C/m. What is the molecular weigh of the solute?

Answer 1

0.62 = 1.86 m

m = 0.333 = moles solute / 0.09983 Kg water

moles solute =0.0332

MM = 2.90 g/0.332 =87.2 g/mol