Suppose a certain person's visual acuity is such that he can see objects

Suppose a certain person’s visual acuity is such that he can see objects clearly that form an image 51 micrometer high on his retina. What is the maximum distance (in meter) at which he can read the 79 cm high letters on the side of an airplane?
Take the lens-to-retina distance to be 2.00 cm.