What are two ways the sentences can be combined correctly?

The students needed to raise money for their school trip. They decided to put on a bake sale.

1.The students needed to raise money for their school trip, and therefore, they decided to put on a bake sale.

2.The students needed to raise money for their school trip, so they decided to put on a bake sale.

3.The students needed to raise money for their school trip; so they decided to put on a bake sale.

4.The students needed to raise money for their school trip and, therefore they decided decided to put on a bake sale.

5.The students needed to raise money for their school trip; they decided to put on a bake sale.