Consider a house into which radon is emitted through cracks in the basement. The total volume of the house is 650 m^3 (assume the volume is well mixed throughout). The radon source emits 250 pCi/s. (A picoCurie [pCi] is a unit proportional to the amount of radon gas and indicates the amount of radioactivity of the gas.) Air inflow and outflow can be modeled as a flow of clean air into the house of 722 m^3/h and an equal air flow out. Radon can be considered conservative in this problem.

-What is the retention time of the house?
-What is the steady-state concentration of radon in the house (units of pCi/L)?