An electric company faces liabilities with present values 24,000 and 1,000, due 7.5 years from now and 20 years from now, respectively.

The company will purchase an n-year zero-coupon bond and a 2n-year zero-coupon bond.

Determine which of the following expressions describes the set of all values of n for which the company can achieve Redington immunization.

• [math]4 \leq n \leq 8[/math]
• [math]5 \lt n \lt 7[/math]
• [math]n=5 [/math] or [math]n=7[/math]
• [math]0 \lt n \lt 5[/math] or [math]n \gt 7[/math]
• [math]4 \leq n \lt 5[/math] or [math]7 \lt n \leq 8[/math]