A seller of health foods is approached by an energy drinks producer to advertise the two products together, because they believe that health foods and energy drinks are complements. What must be true when the health food company estimates the change in quantity demanded of their own service when the price of energy drinks changes, for the two to be indeed complements? Cross price elasticity of demand (Ecp) is positive and greater than 1 Cross price elasticity of demand (Ecp) is negative Cross price elasticity of demand (Ecp) is positive but less than 1 Income elasticity of demand (Ei) is positive