find Efficiency A new high$-$efficiency air filter has been designed to be used in a secure containment facility to do research on detection and destruction of anthrax. Before the filter is built and installed it needs to be tested. It is proposed to use ceramic microspheres of the same diameter as the anthrax spores for the test. One obstacle in the test is that the efficiency of the sampling equipment is unknown and cannot be readily tested because the rate of release of microspheres cannot be sufficiently controlled to define the number of microspheres entering the sampling device. The engineers propose the test apparatus shown in Figure P$-2-10.$ The sampling filters capture the microspheres on a membrane filter that allows microscopic counting of the captured particles. At the end of the experiment, the number of particles on the first filter is $2893$ and the number on the second filter is $76.$ Assuming each filter has the same efficiency, estimate the efficiency of the sampling filters. $($Note: this problem is easily solved by using the particle counts $($C$1,$ C$2,$ C$3)$ and efficiency h$.)$ FIGURE P$-2-10$ Filtration Test Appas