Boolean Equation simlification

[stosw]

Homework Statement

I'm trying to simplify the following to only use XOR and OR gates.

[EQ]x = ab'c'd' + a'd + a'c + a'b[/EQ]

The Attempt at a Solution

My only thought would be to

[EQ]x = ab'c'd' + a'd + a'c + a'b[/EQ]
[EQ]x = ab'c'd' + a'(d + c + b)[/EQ]

But I have no idea what else to do. Can anyone suggest something for me to check into or any tips/hints?

 

[vela]

Use DeMorgan's Laws on (b+c+d).