I am need of help!

the equation 2x^2+cy^2+dx+ey+f=0 represents a conic state the values of c for which each of the following are possible

a) circle

b) ellipse

c) parabola

d) hyperbola

so I am not sure but here is my guess:

a) circle: c=90

b) ellipse: c=50

c) parabola c=?

d) hyperbola c=?

I am not even sure?