If Demand in the United States Is Given by Q₁

if demand in the United States is given by Q₁ = 18,000 - 900p₁, where p₁ is the price in the United States, and if the demand in England is given by 2,000 - 200p₂, where p₂ is the price in England, then the difference between the price charged in England and the price charged in the United States will be

A) $10.
B) $0.
C) $11.
D) $5.
E) $15.