At a room in ahouse, a plywood panel emits formaldehyde at an emission rate of 15000 microg/m2-day and the net area of the panel is 100 ft2. Formaldehyde usually decays to carbon dioxide with a first order rate constant of 0.4/hr. The room has a dimension of 20 ft length, wo ft width and 10 ft height. Average ventillation rate is 2 air changes per hour and the outdoor concentration is 0. Assume that residents of the house have entered the room immediately as the panelling was installed and initial formaldehyde concentration in the room is 0. Estimate (a) maximum concentration of formaldehyde to which the people are exposed (b) time required to reach 90 % of steady state/maximum concentration