In the Hypothetical Situation Considered in Section E17 $x=0$ Plane at Time

In the hypothetical situation considered in section E17.3, the disturbance in the magnetic field that the jostled charged sheet creates on the $x=0$ plane at time $t=T$ reaches position $x=R$ at time

A) $t=T-R / c$ .
B) $t=T$ .
C) $t=T+R / c$ .
D) One cannot answer without more information.