Form 1116 (3)

In turbo tax review, it asked me to input values for form 1116 (3) b and (3)c.  These are the adjusted basis for foreign source income and adjusted basis for total passive activity.  I tried putting in zero for both.  It accepted the zero for (3)b but not for (3)c.  How do I get the value to put in here?  Also, the "zero" for (3) b was probably wrong.  How do I fix that?