The gardening club at school is growing vegetables. The club has 400 square feet of planting beds. Potato plants require 5 square feet of growing space, and tomato plants require 4 square feet of growing space. The students want to plant some of each type of plant and have at least 50 plants. Let p represent the number of potato plants and t represent the number of tomato plants.

a) Write an inequality for the amount of growing space needed.