Implementing a Function Using Multiplexers

[Vishera]

Homework Statement

Homework Equations

The Attempt at a Solution

Here is my solution:

Is this the most efficient solution? I have to minimize the number of multiplexers I use so I think this is optimal, correct?[/B]

 

[.Scott]

Since you're allowed to use 4:1 multiplexers, there is a 3-gate solution. Your last gate (based on X3) is fine. Here's my final clue: How can a truth table be implemented with a multiplexer?