4. (a) Show that \(\sum _ { r = 1 } ^ { 20 } \left( 2 ^ { r - 1 } - 3 - 4 r \right) = 1047675\)
(b) A sequence has \(n\)th term \(u _ { n } = \sin \left( 90 n ^ { \circ } \right) n \geq 1\)
- Find the order of the sequence.
- Find \(\sum _ { r = 1 } ^ { 222 } u _ { r }\)