If 7 * 24 = 25 and 12 * 16 = 20, then what is 16 * 63 equal to?

a * b = √(a² + b²): √(49 + 576) = 25, √(144 + 256) = 20, so √(256 + 3969) = √4225 = 65. (Answer as per the official UPSC answer key.)