Carbon monoxide (CO) combines with the hemoglobin of the blood to form carboxyhemoglobin (COHb), which reduces transport of oxygen to tissues. Smokers routinely have a 4% to 6% COHb level in their blood. The quadratic model 

T = 0.00787x² - 1.528x + 75.89 

approximates the exposure time in hours necessary to reach this 4% to 6% level, where 50 … x … 100 is the amount of carbon monoxide present in the air in parts per million (ppm). (Source: Indoor Air Quality Environmental Information Handbook: Combustion Sources.)

(a) A kerosene heater or a room full of smokers is capable of producing 50 ppm of carbon monoxide. How long would it take for a nonsmoking person to start feeling the above symptoms? Round to the nearest tenth.

(b) Find the carbon monoxide concentration necessary for a person to reach the 4% to 6% COHb level in 3 hr. Round to the nearest tenth.