Please help I am taking a test now. Need answers asap!

Assume that interest rates on 20-year Treasury and corporate bonds with different ratings, all of which are noncallable, are as follows: T-bond - 7.72% A - 9.M% AAA = 8.72% BBB= 10.18% The differences in rates among these issues were most probably caused primarily by. Default risk and liquidity differences. Real risk-free rate differences. Inflation differences. Maturity risk differences Tax effects You plan to invest in securities that pay 6.4 %, compounded annually. If you invest $5,000 today, how many years will it take for your investment to grow to $9, 140.20? 9.82 9.72 11.28 8.85 11.57 Which of the following would be most likely to lead to a decrease in a firm's dividend payout ratio? Its research and development efforts pay off, and it now has more high-return investment opportunities. Its access to the capital markets increases. Its stock price has increased over the last year by a greater percentage than the increase in the broad stock market averages. Its accounts receivable decrease due to a change in its credit policy. e. Its earnings become more stable