E. coli glutamine synthatase is covalently modified by adenylylation(the addition of an AMP group) to specific Tyr resideus. More than one Tyr can be adenylylated on the enzyme, and the number of adenylylated Tyr residues is called the degree of adenylation, symbolized n. Assuming that n=6 to begin, qulitatively describe and justify what will happen to n if

a. atp increasea
b. alpha ketoglutarate/glutamine decreases
c. pi decreases