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 person lent a certain sum of money at 5% per annum at simple interest and in 8 years the interest amounted to $420 less than the sum lent. What was the sum lent?

Option A: 500

Option B: 600

Option C: 700

Option D: 800

Option E: 900
Student:
Option C