Which expression does this power represent?

109


10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10

9 × 9 × 9 × 9 × 9 × 9 × 9 × 9 × 9 × 9

10 × 9 × 10 × 9 × 10 × 9 × 10 × 9 × 10 × 9 × 10 × 9 × 10 × 9 × 10 × 9 × 10 × 9

10 × 9