Identify the semicolon and$/$or colon error$($s$)$ in the following sentences and choose the best revision.

We are enthusiastic about the plan because $(1)$ it is least expensive, $(2)$ its legality is unquestioned, and $(3)$ it can be implemented quickly. Which of the three sentecnes below is correct?

We are enthusiastic about the plan because $(1)$ it is least expensive $(2)$ its legality is unquestioned and $(3)$ it can be implemented quickly.

We are enthusiastic about the plan because $(1)$ it is least expensive, $(2)$ its legality is unquestioned, and $(3)$ it can be implemented quickly.

We are enthusiastic about the plan because: $(1)$ it is least expensive, $(2)$ its legality is unquestioned, and $(3)$ it can be implemented quickly.