If you contribute $250 per month to an RRSP instead of $500 per month, will the time

Question:

If you contribute $250 per month to an RRSP instead of $500 per month, will the time required to reach a particular savings target be (pick one): (i) twice as long? (ii) less than twice as long? (iii) more than twice as long? Give the reason for your choice.