Ten charges are placed on the circumference of a circle of radius R with constant angular separation between successive charges. Alternate charges 1, 3, 5, 7, 9 have charge (+q) each, while 2, 4, 6, 8, 10 have charge (−q) each. The potential V and the electric field E at the centre of the circle are respectively : (Take V=0 at infinity)
a. V=4πϵ0R10q ; E=0
b. V=0 ; E=4πϵ0R210q
c. V=0 ; E=0
d. V=4πϵ0R10q ; E=4πϵ0R210q