On 18 May 1987, the Australian Cabinet approved the final design: Kockums' Type 471 submarine, fitted with the Rockwell system. The contract for construction of six submarines was signed on 3 June and valued at A$3.9 billion in 1986 prices, with allowances for inflation and the changing value of the Australian dollar. The submarine acquisition project was at the time the most expensive project ever undertaken by the Australian Defence Force, but was unseated from this title by the "Anzac"-class frigate project a few years later.