A filter removes 75% of the impurities of water that is passes throught it. Multiple filters can be used together to increase the purity of the water. This situation is represented by A=0.25^N, where...

A filter removes 75% of the impurities of water that is passes throught it. Multiple filters can be used together to increase the purity of the water. This situation is represented by A=0.25^N, where A is the proportion of impurities remaining and n is the number of filters used. What proportion of impurities remians when four filters are used, to the nearest ten thousandth? Explain