When all of the numbers 1, 2, 3, 4, 5, 6, and 7 are placed in 7 boxes with addition or subtraction symbols between them, with one number in each box, the result of the operation obtained is 4.
$$\square + \square + \square + \square + \square - \mathrm { A } - \mathrm { B } = 4$$
Accordingly, what is the product A · B?
A) 15
B) 24
C) 28
D) 30
E) 35