Answer:
an increase in the price of soccer balls.
Step-by-step explanation:
Soccer balls are made of polyethylene and other petroleum oil derivates. An increase in the price of oil will lead to increased price of soccer balls, because the raw material price has gone up.
Kayaks also have raw materials derived from oil that is why they are experiencing a rise in price.
Kayaks and soccer balls will have a directly proportional relationship due to their common raw material source- oil.