Plz help i need help thx brainliest 5 star!!!!!!!!!!!!!

Answer:
Part A: d ≥ 500
Part B: d must be over or equal to 500 but can go infinity at 500+
Step-by-step explanation:
Part A:
≥ stands for "at least" and d has to be "at least" 500,
hence d ≥ 500