An employee's daily 9-hour shift of exposure to acetic acid is as follows:

Time Acetic acid concentration

8:00 am - 10:00 am 6.3 ppm

10:00 am - 11:30 am 12.0 ppm

11:30 am - 12:00 noon 16.0 ppm

1:00 pm - 1:45 pm 4.6 ppm

1:45 pm - 2:00 pm 18.0 ppm

2:00 pm - 6:00 pm 7.0 ppm

1. Calculate the worker's time-weighted average (TWA) exposure concentration based on the sampling duration.
2. Calculate the TWA for compliance testing purposes.
3. Express the calculated TWA concentration of (b) above in mg/m³ acetic acid