The total monthly cost of a basic streaming service plan is modeled by the function C(x) = 2.5x + 15, where x is the number of additional channels purchased outside of the basic plan. When is the cost increasing the fastest? The cost is increasing the fastest when 1 additional channel is purchased. The cost is increasing the fastest when 10 additional channels are purchased. We do not have enough information to answer this. The cost is increasing at the same speed throughout the graph, no matter how many additional channels are purchase