Consider Nutrient contribution per serving

Consider nutrient contribution per serving: 6 ounces of yogurt provides$$350\mathrm{mg}$$of calcium and 80 kcalories$$1/2$$cup of fresh spinach provides$$220\mathrm{mg}$$of calcium and$$3\mathrm{kcalories}$$Calculate the nutrient density for the yogurt and the spinach (make sure you include your units). Which food is more nutrient dense? Why?