Halliday, Resnick & Walker — Force and Motion-I: Problem 54

54 Figure 5-39 shows four penguins that are being playfully pulled along very slippery (frictionless) ice by a curator. The masses of three penguins and the tension in two of the cords are \(m_1 = 12\text{ kg}\), \(m_3 = 15\text{ kg}\), \(m_4 = 20\text{ kg}\), \(T_2 = 111\text{ N}\), and \(T_4 = 222\text{ N}\). Find the penguin mass \(m_2\) that is not given.