3 The \(n\)th term of an arithmetic sequence is \(u _ { n }\), where
$$u _ { n } = 90 - 3 n$$
- Find the value of \(u _ { 1 }\) and the value of \(u _ { 2 }\).
- Write down the common difference of the arithmetic sequence.
- Given that \(\sum _ { n = 1 } ^ { k } u _ { n } = 0\), find the value of \(k\).