One of the customer$-$centric elements of Harrah's Casino's marketing strategy was to segment its customer base. They determined two segments: a segment of high$-$value customers $($who either visited regularly, spent a lot of money when they visited, or both$)$ and a segment of low$-$value customers $($who neither visited regularly nor spent a lot of money during visits$).$ The customercentric approach to these two segments would be to$...$

a$.$ Focus on customer development of both segments.

b$.$ Focus on customer development of a new, undiscovered segment.

c$.$ Focus on customer development of the low$-$value segment.

d$.$ Focus on customer development of the high$-$value segment.