--------------
BB : 2x7=14

B.....B
.......

--------------
BK : 2x7=14

B.....K
.......

--------------
BN : 3x11=33

B.........N
...........
...........

--------------
KK : 1x7=7

K.....K

--------------
NN : 2x13=26

N...........N
.............

--------------

impossible:
KN
QX
RX
--------------