How to find differentiable of rate Practice Test

In chemistry, rate of reaction is related directly to rate constant .

$$\frac{dC}{dt}$=k$ , where is the initial concentration

Give the concentration of a mixture with rate constant $k=$\frac{3}{sec}$$ and initial concentration , seconds after the reaction began.

Given the function inline y=sin(2x)+x^2z+z^3,

find $\frac{mathrm{d}$ y}{mathrm{d} x} at $(x,z)=($\frac{\pi}{2}$,3)$ .