In \odot F, B, C, D, A are on the circle and A C is a diameter. \angle C F D is 4 a - 1 degrees. Find the measure of \angle A F B.
Choices:
A:72
B:108
C:120
D:144
Please directly answer the question and provide the correct option letter, e.g., A, B, C, D.
Question: In \odot F, B, C, D, A are on the circle and A C is a diameter. \angle C F D is 4 a - 1 degrees. Find the measure of \angle A F B.
Choices:
A:72
B:108
C:120
D:144
Please first conduct reasoning, and then answer the question and provide the correct option letter, e.g., A, B, C, D, at the end.
Question: In \odot F, B, C, D, A are on the circle and A C is a diameter. \angle C F D is 4 a - 1 degrees. Find the measure of \angle A F B.
Choices:
A:72
B:108
C:120
D:144