Answer:
57x = 1311
x = 23 hours
Step-by-step explanation:
I don't know how you would model this with two equations but the answer is 23 hours.
If there is such a scalar function <em>f</em>, then



Integrate both sides of the first equation with respect to <em>x</em> :

Differentiate both sides with respect to <em>y</em> :


Integrate both sides with respect to <em>y</em> :

Plug this into the equation above with <em>f</em> , then differentiate both sides with respect to <em>z</em> :



Integrate both sides with respect to <em>z</em> :

So we end up with

Answer:
Option D
Step-by-step explanation:
correct answer on edge :)