(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