A cuboid glass tank has a length of 8dm, a width of 6dm, a height of 4dm, and a water depth of 2.8dm. How many liters of water will overflow the tank if a cube of iron with a side length of 5dm is thrown in?
一个长方体的玻璃缸，长8dm、宽6dm，高4dm，水深2.8dm．如果投入一块棱长为5dm的正方体铁块，缸里的水溢出多少升？
<result>6.4</result>