Alright, let's work through 6243 times 140 step by step
6243 × 140 = 140 × (6243)
+ 140 × 3 which equals 420
+ 140 × 40 which equals 5600
+ 140 × 200 yielding 28000
+ 140 × 6000 what gives us 840000

= 874020
