Apple's iPhone was originally a single model in a product line targeted at high$-$end users. However, lower$-$cost rival smartphones soon entered the market and Apple began to market multiple offerings itself. Here, Apple faces

Multiple Choice

the inability to change prices quickly.

speeding up the diffusion of innovation process.

brand extension confusion.

charging a lower price to gain a foothold in the market.

the challenge of pricing multiple products in an expanding product line.