5. A sequence of numbers \(a _ { 1 } , a _ { 2 } , a _ { 3 } \ldots\) is defined by
$$a _ { n + 1 } = 5 a _ { n } - 3 , \quad n \geqslant 1$$
Given that \(a _ { 2 } = 7\),
- find the value of \(a _ { 1 }\)
- Find the value of \(\sum _ { r = 1 } ^ { 4 } a _ { r }\)