I have quarterly data for iPod, iPhone, and iPad per quarter for 2010 and 2011.

Say data look like this:

iPod
(2010) Q1: 10 Q2: 10 Q3: 10 Q4: 10
(2011) Q1: 14 Q2: 14 Q3: 14

iPhone
(2010) Q1: 15 Q2: 15 Q3: 15 Q4: 15
(2011) Q1: 20 Q2: 20 Q3: 20

iPad
(2010) Q1: 13 Q2: 13 Q3: 13 Q4: 13
(2011) Q1: 15 Q2: 15 Q3: 15


I want to create a stacked bar graph by quarter (4 quarters)
And each quarter, I want to compare 2010 stacked data vs 2011 stacked data.

Truly appreciate it.

Thanks!