Extinction coefficient

The operational definition of an extinction coefficient is that it is the absorbance that a 1M, 1mM or 1uM solution would have. Thus, the mM extinction for reduced cytochrome c at 550nm is 30mM-1cm-1; this solution would have an absorbance of 30 for a 1mM concentration which is impossible to measure (why?) 

o What would be the absorbance or extinction coefficient for a 1 M solution? Could you measure this absorbance? 

o What would be uM extinction coefficient (and yes, units are important in this class)? 

o Could you measure the absorbance of this solution?