Every ordinance which passes the council, in order to become valid, must be presented to the mayor. If the mayor approves it the mayor shall sign it, but if not, the mayor shall return it with written objections to be entered at large upon the journal and proceed to a reconsideration thereof. If, upon reconsideration, five members of the council voting upon a call of yeas and nays favor its passage, the ordinance shall become valid notwithstanding the mayor’s veto. If the mayor fails for 10 days to either approve or veto an ordinance, it shall become valid without mayoral approval. (1957 code § 1.03.070.)