1. Find the equation of the line passing through (0, 4) and having undefined slope.
2. Find the equation of the line passing through the point (1, 4) and having y-intercept (0, 4).
3. Cost Curve A manufacturer has fixed costs (such as rent and insurance) of $2000 per month. The cost of producing each unit of goods is $4. Give the linear equation for the cost of producing x units per month.