Alright, let's work through 5139 times 9987 step by step
5139 × 9987 = 9987 × (5139)
+ 9987 × 9 that results in 89883
+ 9987 × 30 giving us 299610
+ 9987 × 100 yielding 998700
+ 9987 × 5000 producing 49935000

= 51323193
