Alright, let's work through 2540 times 8120 step by step
2540 × 8120 = 8120 × (2540)
+ 8120 × 0 that is equal 0
+ 8120 × 40 resulting in 324800
+ 8120 × 500 producing 4060000
+ 8120 × 2000 producing 16240000

= 20624800
