Definition: You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.
Input: Question: John professes to sell his goods at the cost price but he made use of 800 grams instead of a kg, what is the gain percent?

 Option A: 12 1/3%

 Option B: 12 1/4%

 Option C: 12 2/3%

 Option D: 12 2/1%

 Option E: 12 1/2%

Option E