11. (12 points) If a three-digit number $\overline{\mathrm{abc}}$ (where $a, b, c$ are all non-zero digits) satisfies $\overline{\mathrm{ab}}>\overline{\mathrm{bc}}>\overline{\mathrm{ca}}$, then the three-digit number is called a “Longteng number”. How many “Longteng numbers” are there?