Alright, let's work through 6840 times 3502 step by step
6840 × 3502 = 3502 × (6840)
+ 3502 × 0 producing 0
+ 3502 × 40 what gives us 140080
+ 3502 × 800 resulting in 2801600
+ 3502 × 6000 producing 21012000

= 23953680
