Suppose that producers of softwood lumber will offer to sell 10 million board feet (one inch thick with 12-inch width and 12-inch length) if the price is $2 per board foot, or 15 million if the price is increases to $2.5 per board foot. What is the arc elasticity of supply?

a) 1.6

b) 1.9

c) 1.7

d) 1.8