Xiaogang’s family has a cylindrical fish tank. The diameter of the bottom surface measured from the inside is 30cm. Dad put coral in the fish tank (all immersed in the water, the water did not overflow), and the water surface rose from the original 25cm to 28cm. Please calculate the volume of the coral how many?
小刚家有一个圆柱形鱼缸，从里面量底面直径是30cm，爸爸在鱼缸里放入珊瑚(全部浸入水里，水没有溢出)，水面由原来的25cm上升到28cm，请你计算珊瑚的体积是多少？
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