Mr Mukesh wants to improve his vocabulary. He decides to learn from 2 sources. First, he learns from Norman Lewis Word Power Made Easy and then he learns from GRE 555 word list. After learning from these 2 sources, the number of words he knows becomes thrice his original knowledge. On reading the GRE 555 word list, his knowledge increases twice at the rate at which his knowledge increases by reading Norman Lewis Word Power Made Easy. By how much percent does his vocabulary knowledge increase when he reads Norman Lewis?a) 10%b) 20%c) 30%d) 40%e) 50%