
has gradient

which at the point (-1, 4, 3) has a value of

I'm not sure what the given direction vector is supposed to be, but my best guess is that it's intended to say
, in which case we have

Then the derivative of
at (-1, 4, 3) in the direction of
is

65 times 5 is 325 then u take 1000 and minus 325 from it and end up with 675
A=45
Explanation:
A= a+b/2*h