When iridium-192 is used in cancer treatment, a small cylindrical piece of 192Ir, 0.6 nm in diameter and 3.5 mm long, is surgically inserted into the tumor. If the density of iridium is 22.42 g/cm^3, how many iridium atoms are present in the sample with a volume of 1×10^-15 cm^3? 1×10^-16 atoms, 7×10^7 atoms, 1×10^-15 atoms, or 2×10^-14 atoms?