Please explain where did you find the information? A process involves the removal of oil and other liquid contaminants from metal parts using a heat$-$treat oven, which has a volume of $15,000$ ft$3.$ The oven is free of solvent vapors. The ventilation rate of the oven is $2,100$ cfm$,$ and the safety factor $($K$)$ is $3.$ The solvent used in the process evaporates at a rate of $0\mathrm{.}6$ cfm $($cubic feet per minute$).$ The operator would like to know how long it would take the concentration to reach $425$ ppm$.$