16 + (-16) = 0

Level pending

If a, b, c and d satisfy the equations

$a+ 7b + 3c + 5d = 0\\ 8a + 4b + 6c + 2d = - 16\\ 2a + 6b + 4c + 8d = 16\\ 5a + 3b + 7c + d = -16 \\$

then what is the value of (a+d)(b+c)+ 25?

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