First of all, a <em>supply curve</em> is a chart in Economy that shows us the relation between Price and Quantity of a certain good or service. Several factors may cause this curve to shift to the left or right, e.g.: An increase of customers' purchase power, the decrease of the need for a certain product by the population, and so on...
a. Resource prices rise is another example, and would cause the supply curve to shift to the left. As with it, the final price of the products that depend on this given resource for their production, would rise, hence causing their buyers to purchase fewer quantities of them.
b. If a quota is placed on a good, it would also cause this good's final price to rise, hence causing the consumers to buy less, hence shifting the curve to the left as well.
<em>Note: </em>Of course, these are assuming that the goods in question are <em>non-essential </em>goods. That is, people may choose to buy less of them. In case of essential goods (like toilet paper, or electric power for example), people would still consume it regardless of changes in price! And in that case, the curve would stay still, or even shift slightly to the right, upon a price rise.
