Warranty period difference between Samsung and Dell is 4 months less than the warranty period difference between __and ___?

Study the following information carefully and answer the question given below: Seven Laptop of different brands namely Apple, Hp, Lenovo, Dell, Acer, ASUS and Samsung are kept one over another on different shelves such that the bottom-most shelf is numbered as 1 and the shelf just above 1 is numbered as 2 and so on. Also, the warranty period for each brand is different viz. 12 months, 14months, 15months, 18months, 20months, 21months and 24 months. All the information is not necessarily in the same order. Note: The warranty period of a Laptop is multiple of its shelf number Acer kept 2nd to the above of one which warranty period is an even value. The laptop which has 14 months warranty period is kept immediately below Dell which is placed at an even number shelf. Asus has 21 months warranty period. The warranty period difference between Samsung and Lenovo is four months. At least two LAPTOP brands are kept above HP which is kept above the one which has a warranty period of 20 months but not immediately above. Hp brand LAPTOP  is kept above the 3rd shelf. Apple has either 12 months or 24 months warranty period and is kept immediately below Acer. The difference between Acer and Lenovo warranty period is equal as the number of LAPTOP brands kept below of Apple.