We're going to solve 3991 multiplied by 1440
3991 × 1440 = 1440 × (3991)
+ 1440 × 1 giving us 1440
+ 1440 × 90 that results in 129600
+ 1440 × 900 giving us 1296000
+ 1440 × 3000 producing 4320000

= 5747040
