Part A

On a large lake without waves, how far from shore is a sailboat when the top of its $5-$m mast disappears from the view of a person whose eye height is $0\mathrm{.}9$ m above the water's edge?

Express your answer to three significant figures and include the appropriate units.

View Available Hint$($s$)$

$\backslash [$

d$=$

$\backslash ]$