Alright, let's work through 1399 times 3539 step by step
1399 × 3539 = 3539 × (1399)
+ 3539 × 9 giving us 31851
+ 3539 × 90 resulting in 318510
+ 3539 × 300 which equals 1061700
+ 3539 × 1000 resulting in 3539000

= 4951061
