30. Figure 30 shows a uniform magnetic field B confined to a cylindrical volume of radius R. The magnitude of B is decreasing at a constant rate of 10 mT/s. In unit-vector notation,
(A)the initial acceleration of an electron released at point a (r=5 cm) is (4.4×10⁷ i)m/s².
(B)the initial acceleration of an electron released at point b (r=0) is nonzero.
(C)the initial acceleration of an electron released at point c (r=5 cm) is (4.4×10⁷ i)m/s².
(D)the electric field at point a (r=5 cm) is (+2.5×10⁻⁴ j)V/m.
(E)the electric field at point c (r=5 cm) is (-2.5×10⁻⁴ j)V/m.