He works for 3 months and earns 4182
but it's only asking for 2 months, so the total will be less than 4182
3182×2=6364 which is greater
2788×2=5576 which is greater
2091×2=4182 which is equal
1394×2=2788 which is less
And in those 2 months he earned 2788
so c is the correct answer