Multivariable functions

When mixing $x$ gram molecules of sulfuric acid together with $y$ gram molecules of water, the released heat can be determined by the formula:

$$C(x,y) = \frac{1.786xy}{1.798x+y}$$If initially there are 5 gram molecules of acid and 4 gram molecules of water and we increase them to 5.01 and 4.04, respectively, what is the magnitude of the vector $(x,y,C(x,y))$ that describes this change? Write your answer as a number rounded to three decimal places.

Tip: To express this change, we need to subtract the vector corresponding to the initial state from the vector corresponding to the final state.