15
16
14
17

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Simple logic...

A = 9

B = 8

A and B being the 2 largest numbers in the set

C = 0

D = 1

C and D being the 2 smallest numbers in the set

(C+D) = 1, so any number can be placed in replacement of A and B other than 0 and 1

Then, the highest possible is needed so the 2 largest numbers will replace A and B, numbers 8 and 9

So (A+B) = 17

(8+9) / (0+1) = 17$\boxed{17}$ is the answer