Which equation gives the formal charge (FC) of an atom in a Lewis structure if V is the number of valence electrons in the free atom, N is the number of non-bonding (lone-pair) electrons assigned to the atom, and B is the number of bonding electrons the atom shares?
a) FC=V−(N+B)
b) FC=V−N−2B
c) FC=V−2(N+B)
d) FC=V−2N−B