A 25-turn circular coil of wire has a diameter of $1.00 \mathrm{~m}$. It is placed with its axis along the direction of the Earth's magnetic field of $50.0 \mu \mathrm{T}$, and then in $0.200 \mathrm{~s}$ it is flipped $180^{\circ}$. An average emf of what magnitude is generated in the coil?