case 1
impact = low severity = low then priority= low
case 2
impact = low and severity is medium then priority = low
case 3
impact = low and severity is high then priority = medium
case 4
impact = medium severity = low then priority= medium
case 5
impact = medium and severity = medium then priority = medium
case 6
impact = medium and severity = high then priority = high
case 7
impact = high severity = low then priority=high
case 8
impact =high and severity is medium then priority = high
case 9
impact = high and severity is high then priority = critical