a                         b                       b2
 A      
|-----------------------------|---------------------|-----------------------|
|.-0^2-2-2-2-2---------------.|---------------------|-2-2-2-2-2-------------|
|--0^2-2-2-2-2----------------|-5-5-5-x-x--7-7-7-x-x|-2-2-2-2-2-------------|
|.-0^2-2-2-2-2-5^2--4^2------.|-5-5-5-x-x--7-7-7-x-x|-2-2-2-2-2-5^2-4^2-----|
|----------0-0-----------3b-0-|-3-3-3-x-x--5-5-5-x-x|-------0-0---------3b-0|
|-----------------------------|---------------------|-----------------------|

after you finish b2, play a, then repeat b and b2, then go back to playing a.

listen to the cd so you can see how many times you repeat a.