CONCEPTS: The question applies the concepts of Profit/Loss(Percentage)
SOLUTION:
Let Original SP = 1000
He is selling at 700/-
Profit =20% which implies
CP*1.2 =700
=>CP=700/1.2 = 583.33 [Final CP]
It is sold at 20% less than the actual SP
=>Sold at= (80/100)*1000
=800/- [Final SP]
Profit% =Profit/CP*100
= (SP-CP)/CP*100
=800-583.33 / 583.33 *100
=37.14 OPTION (C)