A mail - order company selling flower seeds charges £3.95 for postage and packing on all orders up to £20 value and £4.95 for orders above £20 value and up to £40 value. For orders above £40 value there is no charge for postage and packing. If you were using equivalence partitioning to prepare test cases f or the postage and packing charges what valid partitions would you define? What about non - valid partitions?