The Average Daily Food Consumption F of a Herbivorous Mammal $F = 0.4 x ^ { 3 / 4 }$

Multiple Choice

The average daily food consumption F of a herbivorous mammal with body weight x, where both F and x are measured in pounds, is given approximately by the equation $F = 0.4 x ^ { 3 / 4 }$ . Find the weight x of an elephant that consumes 400 lb of food per day.

A) 15,000 lb
B) $20,000 \mathrm { lb }$
C) $10,0001 \mathrm {~b}$
D) 5,000 $1 \mathrm {~b}$
E) none of these