Alright, let's work through 1604 times 2303 step by step
1604 × 2303 = 2303 × (1604)
+ 2303 × 4 giving us 9212
+ 2303 × 00 that equals 0
+ 2303 × 600 that equals 1381800
+ 2303 × 1000 that equals 2303000

= 3694012
