Alright, let's work through 3902 times 1440 step by step
3902 × 1440 = 1440 × (3902)
+ 1440 × 2 giving us 2880
+ 1440 × 00 that is equal 0
+ 1440 × 900 yielding 1296000
+ 1440 × 3000 that is equal 4320000

= 5618880
