The following picture shows ethidium bromide-stained DNA bands revealed by gel electrophoresis of the same circular DNA digested in three different tubes containing the following restriction enzyme(s): EcoRI only, BamHI only, or a mixture of the two enzymes. The arrow represents the direction of electrophoresis. (FYI, a restriction enzyme digests DNA by cutting both strands of a specific, short DNA sequence it recognizes.) How many EcoRI and BamHI site(s) are present in this circular DNA