Alright, let's work through 3978 times 2087 step by step
3978 × 2087 = 2087 × (3978)
+ 2087 × 8 which equals 16696
+ 2087 × 70 yielding 146090
+ 2087 × 900 yielding 1878300
+ 2087 × 3000 resulting in 6261000

= 8302086
