since e.g. the Black-Scholes model requires a constant interest rate (flat term structure) but the real world often has normal term structure, I was wondering if it is mathematically correct to
numerically calculate the interest rate r at which an investment in this pseudo-term-structure has the same present-value as investing in the present normal term structure
price the option using Black-Scholes with this pseudo-interest-rate.
Is there something I'm missing or is it even mathematically correct?