1) We need to use one single unit to express the elevation of a person's eyes.
a)
[tex]5^{\prime}6"=5\:feet+6\:inches=66"=5.5^{\prime}[/tex]Remember that 1 foot is equal to 12 inches. And dividing 66" by 12 yields 5.5'
Now, let's plug into the formula we've been given:
[tex]d=1.22\sqrt{5.5}\Rightarrow d=2.86\:miles[/tex]b) Now, let's bear in mind that this same person has reached the top of a mountain, and now he's at 8,000 feet high:
[tex]d=1.22\sqrt{8000}\Rightarrow d=109.12\:miles[/tex]Note that x, is always given in feet, as well as, d is in miles.