query for %notification completed with in the time by priority

Hi..I want to build the query for caculate the required key figures to calculate the % completed on time.

able to show the report will be look like:

for priority A zdownvwend<4 hrs

for priority B zdowntime<8 hrs

for priority C zdowntime<12 hours

these queries will included in web page..

plz its urgent for good answer i will assign points...