$4.[3$ marks$]$ Consider the following pseudocode for an algorithm called $$Algorithm$,$ which reads procedure Algorithm$($a$1,$ A$2,...,$ An: integers$)$ x :$=$ a$1$ for i:$=2$ to n x :$=$ x $+$ ai returns Suppose a list a$1,$ A$2,...,$ An of integers is given as an input. a$)$ Describe what Algorithm$($a$1,$ A$2,...,$ an$)$ returns as output. b$)$ How many times would the expression x :$=$ x $+$ ai be executed? c$)$ Give a estimate for the runtime of this algorithm.