Alright, let's work through 4257 times 7139 step by step
4257 × 7139 = 7139 × (4257)
+ 7139 × 7 resulting in 49973
+ 7139 × 50 giving us 356950
+ 7139 × 200 yielding 1427800
+ 7139 × 4000 producing 28556000

= 30390723
