Please solve it mathematically.

Problem 3 - Chemical release in Ohio. On February 3, 2023, a train derailment in East Palestine, Ohio resulted in the release of about a million pounds of vinyl chloride gas. Vinyl chloride is used to make polyvinyl chloride or PVC. OSHA regulations set limits for vinyl chloride exposure to 1ppm for an 8-hour day, and 5ppm for a 15 - minute exposure. (The Agency for Toxic Substances and Disease Registry (ATSDR) sets chronic exposure limits much lower, at 0.02ppm for between 15 and 364 days). Residents within a 1-mile radius were ordered to evacuate but certainly some did not. If you model a house as a 20,000 ft3 well-mixed box, with fresh air ventilation of 1ACPH (recall this is a volumetric flowrate equivalent to 1 room/house volume per hour). For vinyl chloride under these conditions, 1ppm=1.62107lb/ft3. Assume the vinyl chloride spill is well mixed in the atmosphere, within a hemisphere centered around the spill that is the size of the evacuation area. (While the modeling of a chemical plume is far more complex than we are able to handle at this point, let's try to roughly model this process.) a) Does the indoor concentration of vinyl chloride reach the 5ppm OSHA standard at steady state? b) If so, how long do the people in the house have to shut off their ventilation before the indoor concentration reaches the 5ppm acute exposure limit