Mohsen is going to a party. He will choose at random one shirt from the three shirts and one pair of trousers from the three pairs of trousers in the list below. There are 20 counters in a bag. 4 of the counters are pink. 9 of the counters are white. The rest of the counters are black. Jean takes at random one counter from the bag. (c) Work out the probability that Jean takes a black counter. (2)

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