A #20 propane tank (5 gallon capacity) leaks out into a garage over 24 hours.

A #20 propane tank (5 gallon capacity) leaks out into a garage over 24 hours. If the garage is 20ft x 20ft x 9 ft, and has a K factor of 10, how many ACH are necessary to keep the concentration in the garage below the TLV (2500 ppm)? density of liquid propane is 507.7 g/l, MW = 56.1