Alright, let's work through 8399 times 5457 step by step
8399 × 5457 = 5457 × (8399)
+ 5457 × 9 that results in 49113
+ 5457 × 90 that results in 491130
+ 5457 × 300 resulting in 1637100
+ 5457 × 8000 yielding 43656000

= 45833343
