A student investigated the antimicrobial properties of four concentrations of a novel antibiotic against a culture of Escherichia coli.
Using aseptic techniques, the student inoculated an agar plate with a uniform layer of the bacteria and placed four sterile paper discs (W, X, Y, and Z) on the surface. Each disc was impregnated with a different concentration of the antibiotic. The plate was incubated at 25∘C25^\circ\text{C}25∘C for 24 hours.
The resulting zones of inhibition are shown in the diagram below.
The diameter of each paper disc is 6 mm. The total diameter of the zone of inhibition (including the paper disc) for Disc Y is measured to be 24 mm.
Calculate the area of the agar where bacterial growth was inhibited by the antibiotic from Disc Y (excluding the area of the disc itself). Give your answer to 3 significant figures.
254 mm2254\text{ mm}^2254 mm2
424 mm2424\text{ mm}^2424 mm2
452 mm2452\text{ mm}^2452 mm2
1700 mm21700\text{ mm}^21700 mm2
