Differentiation values: What am I missing here? So, here's the question

$3.$ The movement of an object from a fixed point is measured by the formula:
$y=4x^3+\frac{11x^2}2+2x$
Where $y$ is the distance from the fixed point in miles and $x$ is time in hours.
(i) Calculate the velocity of the object at $x=0$ and $x=2$ hours and interpret the results
(ii) Calculate the acceleration of the object at $x=0$ and $x=2$ hours and interpret the results

So, the question states that the distance(rather displacement) is equal to $4x^3+\frac{11}{2}x^2+2x$, and the differentiated form of this equation, $12x^2+11x+2$ will give the velocity.
Using the value $x$(time)$ = 2$ in the velocity equation gives a velocity of $72$ m/s, thus $s=vt$ so $s=72×2$, $s = 144m$
But plugging $x=2$ into the original undifferentiated equation, which the question states gives the distance, gives a value of $58$.
I feel like I'm missing something really obvious here and I'd like to know what so I don't feel really stupid.
 A: For these types of question it is important to remember the velocity is the rate of change of displacement, and acceleration is the rate of change of velocity. 
That means that the function to find the velocity is the derivative of the function to find displacement.
And the function to find the acceleration is the first derivative of the function for the velocity, or the second derivative for that of the displacement. 
$f(x) = s(t)$
$s(t) = 4s^3 + \frac{11s^2}{2} +2s$
$v(t) = s'(t) = 12t^2 + 11t +2$
$a(t) = v'(t) = 24t + 11t$
Then simply plug in the values of time $0$ and $2$, and you will find your answers, however I'm not sure what is meant by interpret. 
A: I was waiting for others answer but none of them posted so here is the community based answer: 
$$s=4x^3+\frac{11x^2}{2}+2x$$
$$v=12x^2+11x+2$$
As suggested by danimal/Integrator:
$s=vt$ cannot be applied as $v$ is not constant but variable w.r.t. $x$.
At $t=2$ hr 
$$s= 4(2)^3+\frac{11(2)^2}{2}+2(2)=58$$
As suggested by Joelafrite:
$$s = \int \limits^{2}_{0} (12x^2+11x+2)dx $$
$$s = [4x^{3}+\frac{11x^{2}}{2} +2x]^{2}_{0}$$
$$s= 4(2)^3+\frac{11(2)^2}{2}+2(2)=58$$
