Alright, let's work through 4389 times 280 step by step
4389 × 280 = 280 × (4389)
+ 280 × 9 resulting in 2520
+ 280 × 80 which equals 22400
+ 280 × 300 what gives us 84000
+ 280 × 4000 giving us 1120000

= 1228920
