How do you find the null hypothesis when you have the alternative hypothesis?

Which of these tables represents a non-linear function?

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?

One positive integer is 2 less than another. the product of the two integers is 24. what are the integers?