The telephone company wants to add an area code composed of 2 letters to every phone number. In order to do so, the company chose a special sign language containing 224 different signs. If the company used 222 of the signs fully and two remained unused, how many additional area codes can be created if the company uses all 224 signs? Options:	A) 246	B) 248	C) 892	D) 15,128	E) 20,256

Rationale: "# of 2 - letter codes possible from 224 different signs = 224 * 224 . # of 2 - letter codes possible from 222 different signs = 222 * 222 . the difference = 224 ^ 2 - 222 ^ 2 = ( 224 - 222 ) ( 224 + 222 ) = 892 . answer : c ."
Answer: C