A truck drives onto a loop detector and increases the downward component of the magnetic field within the loop from 1.2 × 10-5 T to the larger value B in 0.38 s. The detector is circular, has a radius of 0.67 m, and consists of three loops of wire. What is B, given that the induced emf is 8.1 × 10-4 V?
A. 3.6 × 10-5 T
B. 7.3 × 10-5 T
C. 8.5 × 10-5 T
D. 24 × 10-5 T