Answer:
The uniform annual sales volume of the product for Nadine to be indifferent between the contracts is 7,772 units per year.
Explanation:
We have to compare the present-value of both plans to answer this question.
The Plan A has a present value of $30,000 as is an inmediate payment.
The Plan B has both an annual payment and a royalty, for a span of ten years.
The present value for Plan B is:

This can be simplified with a annuity factor for 10 years, with i=10%.

Then, the PV can be calculated as:

To be indifferent, both present values have to be equal:

The uniform annual sales volume of the product for Nadine to be indifferent between the contracts is 7,772 units per year.