Please help me to compose my letter of inquiry/request.

My professor gave me a failing grade in his subject and I'm writing our dean to request more information about my grades, how my professor graded me. I'm also going to request to give me consideration to pass the subject since I am a graduating student and I cannot afford to enroll this one subject next semester. My professor and I had a misunderstanding in the class and I believe because of that incident, he gave me failing marks