Volume of room = 
= 
Now, according to conversion factor, convert 6,400 mg to micrograms
Since, 1 mg is equal to 1000 microgram.
Therefore, 6,400 mg = 
= 6,400,000 micrograms of acetone.
To calculate concentration of acetone, divide volume and evaporated amount of acetone in micrograms.
Thus,
Concentration of acetone = 
= 39296.5910 microgram per cubic meter or 
Hence, concentration of acetone is equal to 