Which expression is equivalent 121x^2-64y^2 ?

Would this be the correct answer? If not, can you further explain the question?(11x+8y)(11x-8y) 

You have 2 sides that are 2 cms and you have 6 sides that are 1/2 cm and you have 4 sides that are 1 cm. the smallest sides are 1/2 the medium sized sides are 1 and the smallest are 1/2. so to find the perimeter you have to add them all up together so your answer will be 11 cm's