From the first 100 natural numbers, two numbers first a and then b are selected randomly without replacement. If the probability that a - b ≥ 10 is…

From the first $\displaystyle 100$ natural numbers, two numbers first a and then b are selected randomly without replacement. If the probability that $\displaystyle \mathrm{a}-\mathrm{b} \geqslant 10$ is $\displaystyle \frac{\mathrm{m}}{\mathrm{n}}, \operatorname{gcd}(\mathrm{m}, \mathrm{n})=1$, then $\displaystyle \mathrm{m}+\mathrm{n}$ is equal to $\displaystyle \_\_\_\_$.