A group of students draws the field lines for an isolated system consisting of two point charges placed 6cm apart. Their diagram shows the following characteristics:
• Six field lines leave charge M and terminate on charge N.
• An additional six lines leave charge M and extend outward to infinity.
• No field lines originate at infinity and terminate on charge N.
Which configuration of charges is most consistent with the diagram?
a) M=+q,N=−q
b) M=+q,N=−2q
c) M=+2q,N=−q
d) M=−2q,N=+q