using linear interpolation approach deduce YTM for the bonds issued by Nakoli Municipal council

The Finance Director of Nakoli Municipal Council is fantastically incompetent. Unsurprisingly, he issued a prospectus to potential inventors without indicating the yield to maturity (henceforth YTM) of the council's Municipal Bonds. The only information he provided is as follows: (i) the bonds will be for 10 years, (ii) priced at K85 each and will be redeemed at par value of K100, (iii) the bonds will carry an annual coupon rate of 5.5 percent. Investors were left scratching their heads about the YTM of these particular bonds. Luckily, market analysts have observed that similar bonds carry the YTM that hover around 7 and 9 percent