Bobby has been planting blackberries in a garden in his backyard. Bobby started with blackberries in one square foot of garden modeled by the function s(x) = 30. He is allowed to convert more of the garden, and each additional square foot he maintains allows his blackberry plants to produce more by a rate of a(x) = 1.3x-1.
Explain to Bobby how to create an equation to predict the number of blackberries he can expect based on the number of square feet he maintains. Describe how to determine the number of strawberries he will grow with 20 square feet. Use complete sentences.