fixed exam summation ratings

~dev_rating/application/classes/Controller/DeanOffice/Bill.php

@@ -29,7 +29,8 @@ class Controller_DeanOffice_Bill extends Controller_Environment_DeanOffice
 
                 if (!isset($table[$record['StudentID']])) continue; // skip fake
 
-                $rate = ($record['Semester'] + $record['Bonus'] + $record['Extra'] + $record['PreviousExam']);
+                $rate = ($record['Semester'] + $record['Bonus'] + $record['Extra'] +
+                    max($record['PreviousExam'], $record['Exam']));
                 $rateSet = isset($record['Semester']) || isset($record['Bonus'])
                     || isset($record['Extra']) || isset($record['PreviousExam']);
                 $table[$record['StudentID']]['grades'][] = [