The answer is 91
! M+ T$ r8 B2 u# y8 Ftvb now,tvbnow,bttvb1 row 3x4+1x3=15
3 w4 a) E1 \0 U/ K4 x) etvb now,tvbnow,bttvb2 row 4x5+2x4=28
( G1 T J+ V* P8 x( {0 {tvb now,tvbnow,bttvb3 row 5x6+3x5=45
8 d1 t( M h+ }% q9 y4 row 6x7+4x6=66, U9 {! c& C/ N6 H- ^/ A
5 row 7x8+5x7=91  |