Based on your feedback about the calculation of the final mark from assignments and exam the formula has been modified. Given the following abbreviations,
AW = weight of assignments that are at least as good as the exam grade, maximum is 0.35
AG = average grade of the assignments that are at least as good as the exam grade
E = exam grade
the new formula for calculating the final grade is:
Final grade = (1-AW)*E + AW*AG*((E+100)/(118))
Below a chart that compares final grades based on the old scheme, based on the new scheme, and the exam-only grade. The calculations are for the optimal case, i.e., someone that did all assignments (AW=0.35) and got the maximum mark for each of them (AG=30).
Let me know if you have questions or comments.