Januvia is the trade name for sitagliptin, a drug that increases the body's ability to...

Januvia is the trade name for sitagliptin, a drug that increases the body's ability to lower blood sugar levels, and thus it was introduced in 2006 for the treatment of type 2 diabetes. (a) Explain why the five-membered ring in sitagliptin is aromatic. (b) Determine the hybridization of each n atom. (c) In what type of orbital does the lone pair on each N atom reside?