You can solve this equation using one of two approaches:The mertonmodel approach uses single-point calibration and requires values for the equity, liability, and equity volatility (σE).This approach solves for (A,σA) using a 2-by-2 system of nonlinear equations. The first equation is the aforementioned option pricing formula. The second equation relates the unobservable volatility of assets σA to the given equity volatility σE: