A Round Flat Metal Coil Has 180 Turns and Negligible

A round flat metal coil has 180 turns and negligible resistance.It is connected in a series circuit with a
Resistor,with nothing else in the circuit.You measure that a
Current flows through the resistor when a magnetic field through the coil,perpendicular to its area,is changing at
What is the radius of the coil?

A) 0.25 m
B) 0.014 m
C) 0.54 m
D) 0.043 m