Alright, let's work through 4020 times 7539 step by step
4020 × 7539 = 7539 × (4020)
+ 7539 × 0 yielding 0
+ 7539 × 20 which equals 150780
+ 7539 × 000 what gives us 0
+ 7539 × 4000 what gives us 30156000

= 30306780
