The bonds were selling at a premium because the market rate of interest for similar quality bonds was lower than 6.65%.
When bonds are sold at a premium, it means that they are being sold for more than their face value—in this case, 102.8% of the face value. This typically occurs when the coupon rate of the bond (6.65%) is higher than the current market interest rates for similar bonds. Investors are willing to pay more for these bonds because they offer a higher return compared to newly issued bonds with lower rates.