Dominic is a landscape architect and is designing a garden with an area of up to 500 square feet. he will use two types of plants: zinnias and petunias. each zinnia plant requires 1.6 square feet of ground and each petunia plant requires 1.8 square feet of ground. each zinnia plant costs $4 and each petunia plant costs $3, and the architect must spend no more than $600. let z represent the number of zinnia plants and p represent the number of petunia plants. three of the constraints for this situation are z≥0 , p≥0 , and 1.6z+1.8p≤500 . what is the other constraint for this situation? enter your answer in the boxes. __ z + __ p ≤ __