To calculate the callable bond value, use the following formula:
Value of callable bond = Value of straight bond – Call option value
Value of callable bond = 98.5 – 1.25 = 97.25.
Remember: The call option is subtracted from the bond value because the call option is of value to the issuer, not the holder.
As yield volatility increases, the value of the embedded option increases. The formula above shows that for a callable bond, an increase in the option value results in a decreased bond value.