Final answer:
The question lacks sufficient information to calculate the length of arc FA in Circle O as the central angle corresponding to arc FA was not provided.
Step-by-step explanation:
The question involves Circle O with a given radius and angle measures, and requires calculating the length of arc FA. To find the length of arc FA, we need to know the measure of angle FOB, where FOB is the central angle corresponding to arc FA. However, the question does not provide enough information to directly calculate arc FA's length, as it mentions an angle AB and arc BD instead. Since we cannot determine the measure of angle FOB and therefore the length of arc FA with the given information, we are unable to provide a solution.