Suppose that the LIBOR yield curve is flat at 8% with annual compounding. A swaption gives the holder the right to receive 7.6% in a 5-year swap starting in 4 years. Payments are made annually.
The volatility of the forward swap rate is 25% per annum and the principal is $1 million. Use Black's model to price the swaption. Compare your answer with that given by DerivaGem.