President Franklin Roosevelt ordered General Douglas MacArthur in the Philippines to formulate a Pacific defence plan with Australia in March 1942. Curtin agreed to place Australian forces under the command of MacArthur who became Supreme Commander, South West Pacific. MacArthur moved his headquarters to Melbourne in March 1942 and American troops began massing in Australia. Enemy naval activity reached Sydney in late May 1942, when Japanese midget submarines launched a daring raid on Sydney Harbour. On 8 June 1942, two Japanese submarines briefly shelled Sydney's eastern suburbs and the city of Newcastle.

Answer this question, if possible (if impossible, reply "unanswerable"): How many Japanese submarines shelled Sydney on June 8, 1942?
two