1 cubic inch of pure gold weighs 316.598 grams. 24K is about $37.76 per gram.
A cubic foot is 12(316.598) X 12(316.598) X 12(316.598) =
4,606,902,848 grams of gold.
Approximately $173,956,651,540 at $37.76/gram
Check your math again, you would multiple 12^3 X 316.598, then that number by 20 to get the number of total grams, divide that by 31.1 (grams per troy ounce) and multiple by the days spot price.