C(x) = 15x + 75,000
B(x) = 55x

Step-by-step explanation:

C(x) = 15x + 75,000

in problems involving proportions, we can use cross products to test whether two ratios are equal and form a proportion. to find the cross products of a proportion, we multiply the outer terms, called the extremes, and the middle terms, called the means.

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