When each 1 percent hike in the price of pencils causes a 2 percent decline within the quantity of erasers sold, the price crosses elasticity of demand for such complementary goods is about: (1) -2.0. (2) -1.0. (3) -4.0. (4) 2.0. (5) 1.0.
Can anybody suggest me the proper explanation for given problem regarding Economics generally?