4. A sequence \(u _ { 1 } , u _ { 2 } , u _ { 3 } , \ldots\) satisfies
$$u _ { n + 1 } = 2 u _ { n } - 1 , n \geqslant 1$$
Given that \(u _ { 2 } = 9\),
- find the value of \(u _ { 3 }\) and the value of \(u _ { 4 }\),
- evaluate \(\sum _ { r = 1 } ^ { 4 } u _ { r }\).