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Let z 1 and z 2 be two complex numbers such that z 1 + z 2 = 5 and 3 2 3 1 z z + = 20 + 15i. Then 4 2 4 1 z z + equals

1. 75
2. 25 3
3. 15 15
4. 30 3

Correct answer: 75

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