两道很基础的金融数学题,就是题目不太理解,怎么都算不对,答案数字我有,

题目

两道很基础的金融数学题,就是题目不太理解,怎么都算不对,答案数字我有,
A company has debts of $15000 due in six months and $32000 in nine months.Both debts are to be replaced with a single payment in fifteen months.Determine the value of the single payment using a rate of 13.75% simple interest.$ 50,746.88
Determine the value on March 21 of a 90 day note issued on January 30 with a face value of $35000 and a rate of 12.8% if money is worth 11%.（这题就是后面这句if money is worth 11%不太理解）答案：$35,674.61

答案

第一题算式是
15000*(1+.1375*9/12)+32000*(1+.1375*6/12)
因为15000需要付15-6=9个月的利息
同理另一个是6个月
第二题不明白,你有书或者书名么?