(a) Each horizontal number is a multiple of 7.

(b) Each vertical number is a multiple of 7.

(c) The total sum of all the horizontal and vertical numbers is the maximum of all such arrangements satisfying both (a) and (b).

+---+ | | +---+---+---+ | | | | +---+---+---+---+---+ | | | | | | +---+---+---+---+---+---+---+ | | | | | | | | +---+---+---+---+---+---+---+ | | | | | | +---+---+ +---+---+

__Note__: As the figure shows, the bottom row should be considered as two 2-digit numbers rather than a single 4-digit number.