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Mr. Patel, a nutritionist, investigated the relationship between daily water intake (in liters) and energy levels (on a scale of 0 to 10) among his clients. He collected data from several clients, where \(x\) represents the daily water intake and \(y\) represents the energy level. After analysis, he derived the best-fit line equation: \(y = 1.8x + 2.5\). Using this equation, estimate the energy level for a client who drinks 3.5 liters of water daily.