For the information given in the statement you have:
Part A: According to the graph, the point (6,30) means that the total cost of 6 pounds of rice is $30.
Part B: The unit price per pound of rice can be seen in the graph at point (1,4), that is, the price of 1 pound of rice is $ 4.
Part C: To find out how many pounds you would have to buy for the total cost to be $ 20 you have to find the point whose second coordinate is 20, that is, point (4,20), then you would have to buy 4 pounds of rice for the total cost to be $20.