PIMCO gives the following example of an Inflation Linked Bond (ILB), called Treasury Inflation Protected Securities (TIPS) in the US.

How do ILBs work?

An ILB’s explicit link to a nationally-recognized inflation measure means that any increase in price levels directly translates into higher principal values. As a hypothetical example, consider a $1,000 20-year U.S. TIPS with a 2.5% coupon (1.25% on semiannual basis), and an inflation rate of 4%. The principal on the TIPS note will adjust upward on a daily basis to account for the 4% inflation rate. At maturity, the principal value will be $2,208 (4% per year, compounded semiannually). Additionally, while the coupon rate remains fixed at 2.5%, the dollar value of each interest payment will rise, as the coupon will be paid on the inflation-adjusted principal value. The first semiannual coupon of 1.25% paid on the inflation-adjusted principal of $1,020 is $12.75, while the final semiannual interest payment will be 1.25% of $2,208, which is $27.60.

Forecast the semi-annual coupon paid in 10 years based on the bond details given above. The 20th semi-annual coupon, paid in 10 years, is expected to be: