A can derive B, but B cannot derive A. Suppose A is a sufficient condition of B, and A is equivalent to the range of X. If we push from (-2,4) to B, then -a must be greater than-2, and -a is greater than 4, so A is less than -4. Consider whether you can equal the sign. If you have an equal sign, then B is equivalent to the range of X from (-2,4) to A, and A is a necessary and sufficient condition, so you can't have an equal sign. So go to sleep.