Need help Interpreting Vertical Intercept

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I need help with d). I have found the formula to be f(x) = -8 + 880. I know the vertical intercept is 880 but I don't know what it means in the context of this problem. Does it mean the initial cost, the initial demands? I am totally lost and confused about that question.

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I need verification of a) in this problem. Is the formula for the cost of C: f(C) = 42000 + 12x and the formula for revenue is: f(R) = 31x? Please help me with this.

Thank you so much in advance.