For the structure shown below, point A is a pin, point B is a roller, and point C is a roller.

$($a$)$ Using the formula, classify the following beam as statically determinate or indeterminate, and state if the structure is stable. $(5$ pts $)$

$($b$)$ Use the flexibility method and choose proper redundant$($s$).(5$ pts$)$

$($c$)$ Use the flexibility method and determine the reactions for nodes A$,$ B$,$ and C$.(10$ pts$)$

Figure $4$