Michelle has just received an inheritance from her grandfather’s estate. She will be entering college in 3 1/2 years, and wants to immediately purchase three compound- 2 interest investment certificates having the following maturity values and dates: $4000 at the beginning of her first academic year, $5000 at the start of her second year, and $6000 at the beginning of her third year. She can obtain interest rates of 5% compounded semiannually for any terms between three and five years, and 5.6% compounded quarterly for terms between five and seven years. What principal amount should she invest in each certificate?