Consider the following statements :
In water supply distribution network,
1. the grid-iron system requires more length of pipe lines and larger number of cut-off valves.
2. the design of the grid-iron system is difficult but economical.
3. employing a grid-iron system, the dead ends are completely eliminated.
4. employing a grid-iron system permits more water to be diverted towards the affected point from various directions.
Which of the statements given above are correct ?