Question

Which sentence correctly uses commas?

We left the farm after the herd was sold and then the barn was sold for lumber.

We left the farm, after the herd was sold, and then the barn was sold for lumber.

We left the farm after the herd was sold, and then the barn was sold for lumber.

We left the farm after the herd was sold and then the barn was sold, for lumber.

Answer 1

We left the farm after the herd was sold, and then the barn was sold for lumber.

Answer 2

We left the farm after the herd was sold, and then the barn was sold for lumber.

Following copied from: http://www.crosswaterfarm.com/commas/2ic.html#fanboys

Hint : if you use a comma to join two independent clauses, then these and ONLY these conjunctions - or "FANBOYS" - can be used with it.
Here's an example:
Beatrice's hair started smoking in the middle of dinner, and it later burst into flames.
Is the comma justified? The answer can be found by answering two questions:
1) First, check for one of the FANBOYS. Do we have one? Yes: and.
2) The second step, then, is to ask whether what comes on both sides of "and" can stand alone:

"Beatrice's hair started smoking in the middle of dinner" can stand by itself because it's a complete sentence.
So, too, can "It later burst into flames."
Since both sides are independent, the comma is correct.