5. Which of the following statements about the relationship between marginal cost and average cost is correct? A) When MC is falling, AC is falling. B) When AC exceeds MC, MC must be rising. C) AC equals MC at MC's lowest point. D) When MC exceeds AC, AC must be rising.

9. The marginal cost curve intersects the average variable cost curve at 1000 units per day. The rate of output at which average total costs are minimized is A) 1000 units. B) more than 1000 units. C) less than 1000 units. D) none of the above. More information is needed

10. Although isocost lines and budget lines are similar, they differ in that A) budget lines do not have a constant expenditure. B) the consumer is constrained to the budget line while the firm can have more than one isocost line. C) budget lines are linear while isocost lines can be curved. D) the slope of a budget line equals the price ratio while the slope of an isocost line is not related to prices.

Please provide thorough explinations