Get salary details in a Time Calculation rule fast formula

Summary:

We have a requirement to pay an overridden rate when an employee is clocked into a specific payroll type and they also working in a specific location (location is a timecard field/custom attribute). We need to first check the employee's regular rate of pay on the assignment (single assignment model) and only apply the overridden rate for the payroll time type if the regular hourly rate is less than the overridden rate, else the regular assignment rate applies.

What would be the DBI/syntax to pull in the regular rate of pay on the assignment to check to see if it is more/less than the desired overridden rate?