a) (2,3,4)
b) (1,1,1)
c) There are an infinite number of solutions
d) There are no solutions
e) We can't tell without having the system of equations
a) At least two of the equations represent the same plane.
b) The three planes intersect along a line.
c) The planes represented are parallel.
d) More than one of the above choices are possible.
e) None of the above