Answer:

Step-by-step explanation:
A liquid vessel in the form of an inverted regular hexagonal pyramid.
Altitude of pyramid, h = 25 feet
Base edge of pyramid, a = 10 feet

A liquid vessel contain maximum volume 
Change cubic foot to liter


A vessel fill 6,779 liters of water.
6779 lt = 239.398 ft³
Therefore, 

Surface area rise, a = 10 ft , h = 2.764 ft



Hence, The surface rise when 6,779 liters of water is added to vessel will be 265.14 ft^2