Teacher: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.
Teacher: Now, understand the problem? Solve this instance: Question: A grocer purchased 20 kg of rice at the rate of 15 per kg and 30 kg of rice at the rate of 13 per kg. At what price per kg should he sell the mixture to earn 331/3% profit on the cost price?

Option A: 28.0

Option B: 20.0

Option C: 18.4

Option D: 17.4

Option E: None of these
Student:
Option C