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put this solution on YOUR website!First, you want to identify your fixed and variable costs. Your fixed cost is the purchase of the phone. This is a $20 one-time purchase. No matter how many months you need to use your phone, you will only pay this $20 once. On the other hand, you will pay $30 each month you are using the phone so this is your variable cost. Using this information, set up the equation:
C(t) = 30t + 20