Tell whether the situation should be represented by a continuous graph or a discrete graph.

1. the volume of water in a swimming pool steadily decreases by 20 gallons per minute for a period of 3 hours.

2. a bookstore has 12 copies of a best seller. each copy is on sale for $16.00

Continuous graphs are those which allow the x-value to be any point in a given interval. On the other hand, discrete graph allows only certain points to be the values of x in a given interval. 

Both of the given situation above can be represented only by the discrete graph given that each will allow only certain points to be the values of x.