If we have a system X$X$ consisting of subsystems X1$X_1$ and X2$X_2$.
We also know that X1$X_1$ and X2$X_2$ have eigenstates H1 = 1 * 10 20$H_1 = 1 \times 10^{20}$ and H2 = 1 * 10 22$H_2 = 1 \times 10 ^{22}$.
Can we calculate the entropy given the above data? If yes, what's the basis?