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A thief has 4 bunches of master keys each having 5 keys. He plans to open the master lock of a bank. The master lock has 3 key holes. The ‘lock’ opens only if the relevant keys are inserted in the respective key holes and opened. Assuming that all the 3 keys holes use unique keys and the thief has only one set of relevant keys in the bunches, how many futile attempts he would have to make before he succeeds in opening the master lock?