Can I please get some help with this?

An evaluation of an employee's current exposure by determining the employee's exposure to hexane (toxic contaminant) by calculating time-weighted average (TWA) and compare it to the permissible exposure limit (PEL) and modify the PEL, if necessary. If it is necessary to modify the PEL, explain the reasoning why it is to be modified. Once the current exposure has been determined, select the appropriate ventilation system between dilution and local exhaust that is the best choice to control the concentration of the contamination. Ensure that you provide the reasons why you think your selection of ventilation system is the best choice

Scenario

An employee working in a room measuring 15 ft x 20 ft x 15 ft sprays paint assembly parts using a paint containing hexane. The PEL for hexane is 500 ppm. The employee wears a half-face, air-purifying respirator, but management would like to install engineering control measures to reduce or eliminate the employee's exposure to hexane. The options are to:

(1)install a dilution ventilation system, or (2)install a local exhaust ventilation system.

The employee works a 9-hour shift and has the following exposures:

Sample No. Concentration Sampling Time 550 ppm 1.5 hours 2 400 ppm 5.8 hours 3 375 ppm 1.7 hours