A researcher captured a transmission electron micrograph (TEM) of a mitochondrion from a cardiac muscle cell. The image was viewed at a magnification of ×12,500\times 12,500×12,500. Using a ruler, the researcher measured the maximum length of the mitochondrion image to be 4.5 cm4.5\text{ cm}4.5 cm.
Calculate the actual length of this mitochondrion. Give your answer in micrometres (μm\mu\text{m}μm).