A Merry-Go-Round Has an Area of 300 M² and Spins

Multiple Choice

A merry-go-round has an area of 300 m² and spins at 2 rpm about a vertical axis at a place where the Earth's magnetic field is vertical and has a magnitude of 5 *10^-5 T. The emf around the rim is:

A) 0
B) 0.5 mV
C) 3.1 mV
D) 15 mV
E) 30 mV