Help: Required for SLA calculating formula

Hello All,

Need formula for calculating SLA

My SLA requirements:

Priority 3: 24 Hrs. (1 Business day)
Priority 4: 48 Hrs. (2 Business days)
Priority 5: 120 Hrs. (5 Business Days)

I need the SLA report whether SLA MET OR SLA NOT MET... using the priorities in column D...

1. SLA should be calculated using COULMN P and Column O (Pending Closed DT - Registered DT)
2. IF the SLA is not in the above step then SLA should be calculated from COULMN Q and Column O ( Restored DT - Registered DT)
3. The SLA should be calculated using the priorities in column D
SLA report should also have any option to add holidays if any... and the work hours are 24 HRS Monday to Friday (24 x 5)