Help with Exceptions

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I have made a copy of report id 9 (responded) and have added a drill down level.

Within the drill down level, I have columns for the incident ref no and subject.

I am trying to add the following exceptions to color code, and can't seem to find the correct expressions.

I need the following exception criteria.

1. Incidents responded to within “less than or equal to”  8 hours
2. Incidents responded to within  “greater than" 8 and "less than or equal to" 12 hours
3. Incidents responded to within “greater than” 12 hours and "less than or equal to" 24 hours
4. Incidents responded to within "greater than" 24 hours