Consider CTI only (to make the problem smaller):
Part Time (1 to 11 hrs.): $335.00/per hour
Full Time (12 to 18 hrs.): $17,820.00
* Credit hours over 18 are charged at the part-time rate
Part time (1 to 7 hrs.): $520.00/per hour
Full time (>= 8 hrs.): $520.00/per hour
Create a decision table for this problem. In my solution I was able to reduce the number of rules from 16 to 4.