Discs carrying 10-fold serial dilutions of antibiotic are placed on a lawn of bacteria to find the lowest concentration that will inhibit growth of the bacteria. bacterial growth appeared up the edge of the first (1/10) and second dilution disc (1/100), but a 20-mm zone of clearance appeared around the third dilution disc (1/1,000). if resistance is defined as no zone of clearance, what is the resistance titer of the antibiotic for this organism?