Answer:
the extra money causes a 50% increase in IPhone sales.
Step-by-step explanation:
One example would be that the extra money causes a 50% increase in IPhone sales. Therefore this higher income is shifting the demand curve for IPhones upwards due to the number of individuals purchasing the product. If individuals come into more money than they need to survive it is usually spent on luxury goods/services. This creates a demand for these goods and services that did not exist at the same level previously. This increased demand is what curves the demand curve upwards.