i=dQ/dt
ir = 3C/2.0s = 1.5A ;; current due movement of charge Qr
il = -0.625C/4.5s = -0.138 A ;; current due movement of charge Ql
to find net current you need to establish some references such as reference direction, and time.
for example if both charges start moving at the same time and positive current direction is to the right then:
iNet = ir + il ;; but we need to observe direction convention so...
iNet = ir + il = 1.5A + (-0.138 A) = 1.361 A
