Which of the following begins the two main parts of a direct proof of a∪(b∩c) = (a∪b) ∩ (a∪c)?
1) Assume a∪(b∩c) = (a∪b) ∩ (a∪c) and prove a⊆(a∪b) ∩ (a∪c) and (a∪b) ∩ (a∪c)⊆a
2) Assume a⊆(a∪b) ∩ (a∪c) and prove a∪(b∩c) = (a∪b) ∩ (a∪c)
3) Assume (a∪b) ∩ (a∪c)⊆a and prove a∪(b∩c) = (a∪b) ∩ (a∪c)
4) Assume a∪(b∩c) = (a∪b) ∩ (a∪c) and prove (a∪b) ∩ (a∪c)⊆a