Do You Know Biggest Impact On Retirement Savings?

Adapted from Kiplingers 10/2010, chart 50, taken from Fiduciary Benchmarks.

A QUIZ:

First the assumptions:

-45 years old
-earning $50,000/year
-contributes 6% of pay and employer matches 50%
-investment return equals 6%/year
-retires at 65

Suppose he can do one of the following:
1. work 2 more years, i.e. until he is 67 years old,
2. increase saving rate from 6% to 10%,
3. increase return from 6%/year to 8%/year.

Which of the 3 do you think would have the biggest impact on his retirement savings?