Instructions: In this task, you need to answer the given multiple-choice question on the gain. Gain is the value by which to multiply the input. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
Input: Problem: a dishonest dealer professes to sell goods at the cost price but uses a weight of 800 grams per kg , what is his percent ? 
Options: a ) 25 % , b ) 25 % , c ) 29 % , d ) 55 % , e ) 45 %
Output:
b