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.
Q: Question: How long will it take for a sum of money to grow from Rs.3000 to Rs.18,000, if it is invested at 5% p.a simple interest?

Option A: 8 years

Option B: 64 years

Option C: 100 years

Option D: 56 years

Option E: None
A:
Option C