L = 2h - 207
so
L^2 = (4 h^2 - 828 h + 42849)
(1/3) L^2 h = 91,394,008
(1/3)(4 h^3 - 828 h^2 + 42,849 h )= 91,394,008
4 h^3 - 828 h^2 + 42,849 h - 274,182,024 =0
try h = 450
364,500,000 - 167,670,000 + 19,282,050-274,182,024 =-58,069,974
try h = 475
428,687,500 - 186,817,500 + 20,353,275 -274,182,024 = -11,958,749
try h = 480
442,368,000 - 190,771,200 + 20,567,520 - 274,182,024 = -2,017,704
graph these and look for where it hits zero, probably around 481 ft