5. (i)
$$U _ { n + 1 } = \frac { U _ { n } } { U _ { n } - 3 } , \quad n \geqslant 1$$
Given \(U _ { 1 } = 4\), find
- \(U _ { 2 }\)
- \(\sum _ { n = 1 } ^ { 100 } U _ { n }\)
(ii) Given
$$\sum _ { r = 1 } ^ { n } ( 100 - 3 r ) < 0$$
find the least value of the positive integer \(n\).