Which of the following statements are correct?

1. In double row housing, either the cattle face out from each other (tail-to-tail system) or face in towards each other (head-to-head system).
2. When the number of animals doesn’t exceed 10, the double row system is desirable.
3. Animals get fresh air directly and the milking process can be effectively supervised in Tail to Tail system.
4. Sun rays reach the gutter, and provide better sanitation in Head to Head system.