Final answer:
The question appears to be regarding the required fire extinguisher rating for a vehicle power unit, but instead presents a scenario involving the effect of temperature on the pressure inside a fire extinguisher. In reality, the fire extinguisher should meet the necessary safety standards for the specific vehicle, and as temperature increases, so does the pressure inside a CO₂ extinguisher.
Step-by-step explanation:
The question refers to the required fire extinguisher rating for a power unit of a placarded vehicle. The rating that specifies the classes of fires an extinguisher is designed to fight must meet legally mandated requirements based on the potential hazards encountered in the power unit. However, your question seems to be oriented towards the physical behavior of a fire extinguisher under specific conditions, rather than the regulatory fire extinguisher rating. For a typical fire extinguisher filled with CO₂, as the inside temperature of a vehicle increases, so does the pressure inside the extinguisher. To determine the internal pressure of the fire extinguisher after being left in a hot car, one must use the ideal gas law to make the calculation. Since this is a hypothetical situation, instead of providing the exact fire extinguisher rating required by regulations, I can help you understand the concept that as temperatures rise, the pressure inside the extinguisher will also increase accordingly.