A group of five friends have the habit of collecting stamps. The stamp collections of "Day \(1\)" and "Day \(2\)" are given below as a bar graph. Analyse the graph and answer the following questions.
1. How many stamps Arun collected on both days?
2. How many of them collected less than \(15\) stamps on the first day?
3. What is the average collection of all stamps collected on Day \(2\)?
4. What is the ratio of the total collection of stamps of Neha and Diksha for both days?