Coefficient in front of x^2 is 0.4. What that means is that for same increase of x now we will have less increse of y. If you picture that we can also say that graph would be wider. The graph will stay on positive side of y axis because x^2 is always positive and 0.4 times that is again always positive.
The answer is third graph (middle one)
The answer would be -8/27 I believe
Given a vetex (h,k) of a function parabola, the corresponding equation is:

With (h,k)=(2,5) we get the equation:

In order to find a, we use the given point (3,7) like this:

The equation is then: