Finding the molar mass from an Osmotic Pressure

[bkdem]

An unknown, non-ionizing compound with a mass of 0.108 g is dissolved in water to make 100.0 mL of solution. If the solution has an osmotic pressure of 0.169 atm at 20.8 ºC, what is the molar mass of the substance?
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The answer is 154.1g/mol. I got this question wrong and can't figure out how I'm getting a different answer.

Steps I took:
π=iMRT and M=π/iRT
Knowns: i=1, R=0.0821 L-atm/mol-K, T=20.8ºC+273.15= 293.95K, π=0.169 atm

1. Molarity= (0.169)/(1 * 0.0821 * 293.95) = 4.07 mol/L
2. 100.0 mL = 0.1L
3. moles unknown = 4.07 mol/L * 0.1L = 0.407 mol
4. molar mass = g/mol = 0.108g/0.407mol = 0.265g/mol

What am I doing wrong?