Which is the electron configuration for lithium?
O 1s2
O 2s3
O 1s?2s!
O 1s'2s?

The answer is c - the principal of original lateral continuity. 

Rate law for this reaction israte of the reaction = k[a]²[b].second order in a  means concentration of a in power of two, and  first order in b means concentration of b in power of one.