m gettin d answer as 45
middle digit sum nos
1 2 (1,1) (2,0) ----- 2
2 4 (4,0)(3,1)(3,1)(2,2)-------4
3 --------6
4 ------------------------------------8
5---------------------------------------------------------------------9
6 -------------------------------7
7 ----------------------------------------5
8 ----------------------------------------3
9 ---------------------------1
addin them u get 45