Quant Interview Practice Questions

You are tasked with pricing a payer swaption. This swaption gives the holder the right, but not the obligation, to enter into a swap agreement where they pay a fixed interest rate and receive a floating interest rate (typically LIBOR). The underlying swap has a tenor of 5 years and the swaption expires in 2 years. Which of the following models is most commonly used for pricing such European-style swaptions in the financial industry, assuming a log-normal distribution of the underlying swap rate?