Answer the following question: Information:  - The Prime Minister of the Commonwealth of Australia is the head of government in Australia. The individual who holds the office is the most senior Minister of the Crown, the leader of the Cabinet and the chairperson of the National Security Committee. The office is not mentioned in the Constitution of Australia and exists only through an unwritten political convention and tradition. Despite this, in practice it is the most powerful parliamentary position in Australia. The individual who holds the office is commissioned by the Governor-General of Australia.  - The Australian Labor Party (ALP, also Labor, was Labour before 1912) is a political party in Australia. The party has been in opposition at federal level since the 2013 election. Bill Shorten has been the party's federal parliamentary leader since 13 October 2013. The party is a federal party with branches in each state and territory. Labor is in government in the states of Victoria, Queensland, South Australia, and in the Australian Capital Territory and Northern Territory. The party competes against the Liberal/National Coalition for political office at the federal and state (and sometimes local) levels.  - Robert James Lee "Bob" Hawke (born 9 December 1929) is an Australian politician who was the Prime Minister of Australia and the Leader of the Labor Party from 1983 to 1991.  - Federal elections were held in Australia on 24 March 1990 . All 148 seats in the House of Representatives and 40 seats in the 76 - member Senate were up for election . The incumbent Australian Labor Party led by Bob Hawke defeated the opposition Liberal Party of Australia led by Andrew Peacock with coalition partner the National Party of Australia led by Charles Blunt .  - William Richard "Bill" Shorten (born 12 May 1967) is an Australian politician who is the current Leader of the Opposition in the Parliament of Australia, in his capacity as Leader of the Australian Labor Party, after being elected party leader at the 2013 Labor leadership ballot. Shorten led Labor at the 2016 federal election at which the Liberal/National Coalition retained majority government.     What object entity has the relation of 'office contested' with the subject 'australian federal election'?   Choices: - chairperson  - leadership  - prime minister  - prime minister of australia
Answer:
prime minister of australia