Radioactive radon gas (222Rn) enters an average building at a rate of 5 picocuries per second per square meter of foundation area. Consider a house with a foundation of 400 square meters and a volume of 1000 cubic meters. Assume the house if well designed for energy conservation so that the ventilation rate is low and only one tenth of the air in the house is exchanged with outdoor air every hour. What will be the average steady state concentration of 222Rn (in Ci/cubic meter) in the house?