For a general quartic equation ax4 + bx3 + cx2 + dx + e = 0 with real coefficient a, b, c, d and e, find, if possible, the relationship between a, b, c, d and e so that the roots of the equation satisfly one of the following conditions respectively:
(a) all roots are not real
(b) only two roots are real
(c) all roots are real
If impossible, please explain in detail why it is impossible.