Answer:
I and II are true
Step-by-step explanation:
I. Increases in the demand for a good, which is produced by a competitive industry, will raise the short-run market price
In the short run of the competitive industry when the market demand for goods rises then the price of these goods will also increase. This is because the price equals marginal revenue. Therefore, when price rises then marginal revenue will increase and as a result, the marginal cost curve moves up and firms produce more quantity of goods. This statement is therefore true.
II. Increases in the demand for a good, which is produced by a competitive industry, will raise the long-run market price
The effect of the increase in goods demand is the same in the long run of the competitive industry as it is in the short run. Therefore, a rise in demand would raise the price of the goods above ATC (Average Total Cost). Hence, the above statement is also true.