You want to image a slice that is 5cm off-center along z-axis. When the strength of the slice selection gradient is 0.2 G/cm, what is the difference between the transmission frequencies for excitation of the 5cm off-center and the isocenter (0cm off-center)? (Hint : γ^=γ/2π = 42.58MHz/T = 4258 Hz/G)