Answer: 0.
Step-by-step explanation:
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: i got 44 for the answer
she had 98 but spent 10.85 so she now has:
98-10.85 = 87.15
skateboard cost 64
87.15 -64 = 23.15 is what she can spend on cookies
23.15 / 1.65 = 14.03 she can't buy more than 14 cookies
so answer is c. n ≤ 14