The energy of the probe field causes protons to flip when in a
1.50000 -T magnetic field. $A \pm 0.001-$ T variation in the magnetic field causes a mismatch with the radio frequency flipping field and no flipping at a distance of 0.002 $\mathrm{m}$ from where the magnetic field is matched to the flipping field. Which answer below is closest to the change in the $B$ field per unit distance?
(a) 0.08 $\mathrm{T} / \mathrm{m}$
(b) 0.8 $\mathrm{T} / \mathrm{m}$
(c) 8 $\mathrm{T} / \mathrm{m}$
(d) 0.003 $\mathrm{T} \cdot \mathrm{m}$
(e) 0.000003 $\mathrm{T} / \mathrm{m}$