For natural numbers $a , b$, let P and Q be the points where the curve $y = a ^ { x + 1 }$ and the curve $y = b ^ { x }$ meet the line $x = t ( t \geq 1 )$ respectively. Find the number of all ordered pairs $( a , b )$ satisfying the following conditions. For example, $a = 4 , b = 5$ satisfies the following conditions. [4 points]\\
(가) $2 \leq a \leq 10, 2 \leq b \leq 10$\\
(나) For some real number $t \geq 1$, $\overline { \mathrm { PQ } } \leq 10$.