Question B2: The situation is not quite as simple when we allow negative numbers. (a) Suppose that we know -5 < x < 7 and -8 < y < 6. Give lower and upper bounds for the product xy. Show your work. (b) Suppose instead that we know −5 < x < 7 and −4 < y < 6 (someone has made a better estimate for y). Give revised lower and upper bounds for the product ry. Show your work. (c) Suppose that we know -a < x < b and -c < y <d, with a, b, c, and d all positive numbers. Is it possible to give a formula for lower and upper bounds on ry in terms of a, b, c, and d?