Lesson 10: use of 'pi' as a variable

[labarba]

This needs to be changed. We should not use a variable 'pi' to mean a panel, because this keyword should be reserved for 3.1415...

[mesnardo]

[Lesson 09] the variables 'pi' and 'pj' have been replaced by 'p_i' and 'p_j', respectively.