16. Infinite Bank sells an equity-linked CD. The maturity of the CD is 4 years. The CD guarantees to return the initial amount invested plus X% of the percentage increase in the S\&P500 index over the 4 year period. The value of the S\&P500 at issue of the CD is 1200 . 4 years later the value is 1440 . The purchaser of the CD invests $5,000 and receives $5,700 at the end of the 4 years. Find X%