VTMO 2016 — Grade 7 — final Question 1

$A = 3 \times 4$ grid has $- 8 , 1 , - 1 , - 2$ prefilled as shown. Remove one of $0 , 2 , 3 , 4 , 5 , 7 , 8 , 10 , 11$, and fill the eight remaining cells so every row and column has the same average. Explain.