(30 points) For this problem, assume that people are trapped in the southeast stairway above the 12th floor when smoke enters that stairway at the 12th floor. Assume the smoke in the stairway has the following uniform composition throughout the stairway as a function of time:

CO concentration increases linearly from 0 ppm at t=0 to 6000 ppm at t=2 minutes, remains at 6000 ppm until t=10 minutes and then decreases linearly back to 0 ppm at t=12 minutes

CO2 concentration increases linearly from 0 % at t=0 to 2% at t=2 minutes, remains at 2% untilt=10 minutes and then decreases linearly back to 0% at t=12 minutes.

Based on these conditions, determine the following:

a. (10 points) The calculated time, to the nearest minute, to incapacitation of people attempting to descend within the stairway above the 12th floor. If incapacitation does not occur, discuss why.

b. (10 points) The calculated time, to the nearest minute, to lethality for people attempting to descend within the stairway above the 12th floor. Assume people stop moving once they have become incapacitated, as calculated in part a. If lethality does not occur, discuss why.

c. (10 points) The calculated time, to the nearest minute, to incapacitation for people trying to ascend in the stairway in order to move further away from the 12th floor once they realized they were trapped in the stairway. Explain why this answer is or is not different from your answer to part (a).