pls help worth 25 points the question is on the image btw the answer is 15 cm high Just explain how it is done

Answer:
steps below
Step-by-step explanation:
volume of rock : 16 * 12 * 12 = 2304
height will take when it was threw into tank: 2304 / (32*24) = 3
Original water height + rock height: 12 + 3 = 15 cm