The distance to the visible horizon varies directly with the square root of the height

of the observer above sea level. An observer 1.8 m tall can see 4.8 km out to sea when

standing on the shoreline.

I know how to do it but the answers says I'm wrong...

<--- this is meant to be proportional sign but I can't seem to find it and alpha looks close enough xD

so

k=3.57771

we found k then:

but the answer is like 8. something