To find the elevation at the bottom of Lake Segundo, we first find its depth based on the depth of Lake Profondo.
Since Lake Profondo has a depth of 84 feet and Lake Segundo is 5.6 times deeper, we can calculate the depth of Lake Segundo as follows:
\[ \text{Depth of Lake Segundo} = 84 \text{ feet} \times 5.6 = 470.4 \text{ feet} \]
Assuming that the elevation at the surface of both lakes is at sea level (0 feet), the elevation at the bottom of Lake Segundo would be:
\[ \text{Elevation at the bottom of Lake Segundo} = 0 \text{ feet} - 470.4 \text{ feet} = -470.4 \text{ feet} \]
Thus, the elevation at the bottom of Lake Segundo is -470.4 feet (below sea level).