My School requiring 90% on final

I am in my last mod, and never in the past year and a half were we told that we needed a 90% course grade + a 90% on the final. I passed my last course with an 87 and final with an 86. Yea it said we needed a 90 on the syllabus but they are now making me retake the entire last mod and spend more money in order to pass. What can I do?