sentences:  The company did not add another permanent hamburger to its menu until the introduction of the Big King sandwich in 1996 in response to McDonald's Big Mac sandwich.The company began experimenting with premium hamburgers, made from higher quality ingredients, in 1978 with the introduction of its Specialty Sandwich product line.The products were some of the first designed by a fast food restaurant chain that were intended to capture the adult market, members of which would be willing to spend more on a higher-quality product.