Assume that in the market for slices of cheese pizza in New York City, the quantity demanded at a price of $3 per slice is 20,000 slices/hr. If that's the case, which number makes the most sense as the quantity demanded per hour at a price of $4 per slice?

A. 30,000

B. 15,000

C. an infinite price

D. 20,000

Need explanation typed calculation only.