UV curable epoxy resins are used in sealing, in gap filling, and as a clear coating. Your boss saw a report submitted by the chief financial officer (CFO) that said the equivalent annual worth of maintaining the equipment used in producing the resins was $48,436 over the last 5 years. The report showed that the cost in year 1 was $42,000, and it increased arithmetically by $4000 each year. Your boss thought $48,436 was too high, so she asked you to determine what interest rate the CFO used in making the calculations. What was the interest rate?