The sum of the first four terms of an AP is 28 and sum of the first eight terms

The sum of the first four terms of an AP is 28 and sum of the first eight terms of the same AP is 88. Sum of first 16 terms of the AP is

2) 1,8,15,22,29,36,… is

3) In a certain AP, 5 times the 5th term is equal to 8 times the 8th term, then its 13th term is equal to

4) The sum of the first ten terms of an AP is four times the sum of the first five terms, then the ratio of the first term to the common difference is

5) A number 15 is divided into three parts which are in AP and sum of their squares is 83. The smallest part is