Show me the steps to solve key chains

To make key chain$$s$,$ there is an initial$$ set$-$up cost of $$$$537.$ It also costs $$$$0\mathrm{.}27$ per key chain for materials and labor.$$

$$a$.)$Letting x represent the number of key chains $$made$,$ what will be the total cost function$$ C$($x$)?$

$$C$($x$)=$

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$$b$.)$If we sold each key chain for $$$$0\mathrm{.}70,$ what will be the total revenue function$$ R$($x$)?$

$$R$($x$)=$

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$$c$.)$What is the smallest number of key chains needed to be sold in order for the total revenue to be at least the total cost necessary to make$$ them?

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