1. The sum of the first 40 terms of an arithmetic sequence is 3220. The first term is 2.5. Find the common difference.
2. The first term of an arithmetic sequence is 5, the common difference is 0.8. Find the sum of the first 250 terms.
3. Suppose I borrowed $1,000 from my neighbor The Saver, and I am paying the loan off in 4 months with a payment amount of $821 per month. What is the simple annual interest rate The Saver is charging me? Round answer as a percent to a whole number (for example, if the answer is 52.66666%, enter 53).
4. Suppose I need to borrow $1,428 from my neighbor The Saver. The Saver charges 138% simple annual interest rate and I have to pay the principal plus interest off in 16 equal monthly payments. How much will be the monthly payment amount? Round answer to two digits after the decimal point.

5- The 5thterm of an arithmetic sequence is 6, the common difference is 3.4. Find the 18thterm.