The ANSI ASC $x_{12}N837$ is a:

a$.$ series of fixed$-$length records that is used to bill institutional services, such as services performed in hospitals

b$.$ flat file format that is used to bill physician and noninstitutional services, such as services reported by a general practitioner on a CMS$-1500$ claim

c$.$ variable$-$length file format that is used to submit institutional, prohessional, dental, and drug claims

d$.$ unique $11-$digit, three$-$segment number, which identifies a vendor, product, and trade package size