Abraham conducts research on how a new product captures the attention of cAkeem designs customized automobiles for his clients. He meets them to understand their unique requirements and creates models that fit their specifications. He has designed and sold hundreds of customized vehicles, each distinctive in its own way. In this scenario, which of the following marketing plans is Akeem using?

a$.$ One$-$to$-$one marketing

b$.$ Concentrated marketing

c$.$ Differentiated marketing

d$.$ Undifferentiated marketing