Alright, let's work through 8420 times 3370 step by step
8420 × 3370 = 3370 × (8420)
+ 3370 × 0 that equals 0
+ 3370 × 20 which equals 67400
+ 3370 × 400 that is equal 1348000
+ 3370 × 8000 that results in 26960000

= 28375400
