I played around with it for a little bit. It's extremely complicated and conditional on a more than just a few things.
For example, if you miss two shots the entire time, there are three possible outcomes: (calculations are for total score)
1a) miss your first two shots: (2*0)+(1*7.5)+(17*15)=262.5
1b) miss your last two shots: (2*0)+(1*7.5)+(17*15)=262.5
1c) miss your first and last shots: (2*0)+(1*7.5)+(17*15)=262.5
2a) two consecutive misses, but not on first two or last two shots: (2*0)+(2*7.5)+(16*15)=255
2b) two non-consecutive misses, one on first shot, the other not your last shot: (2*0)+(2*7.5)+(16*15)=255
2c) two non-consecutive misses, one on last shot, the other not your first shot: (2*0)+(2*7.5)+(16*15)=255
3) two non-consecutive misses, neither on first or last shot: (2*0)+(3*7.5)+(15*15)=247.5
I may have left some scenarios out, but this gets even more complicated as the number of misses increases, since there are more possible combinations of consecutive misses, non-consecutive misses, consecutive misses on first/last shots, non-consecutive misses on first/last shots, etc.