Every contract and all bonds and instruments to which the city is a party and which are approved by the city council must be signed and be executed in the name of the city by the mayor and the city manager. Every contract to which the city is a party, but for which council approval is not required pursuant to Section 6.07 due to the dollar amount, or otherwise sought, must be signed and be executed in the name of the city by the city manager; except for those contracts the approval of which has been delegated to city department heads and to the assistant city manager pursuant to Section 6.07. All contracts, irrespective of dollar amount, must be signed by the city attorney prior to execution; except for those contracts the review and approval of which has been delegated to a licensed attorney in the city attorney’s office pursuant to Section 6.07.