Implement XNOR using NAND gates ?

[rclakmal]

what is minimum number of NAND gates to implement XOR?
i thought it in this way .first i found how many NAND gates are need to to implement XOR .
if the two input it 'A' nd 'B'
then
XOR function =A'B+AB'
so i need two NAND gates to invert A and B
then for two AND gates i need another 4 NAND gates as each AND gate need 2 NAND gates .
then for final OR gate i need another 3 NAND gate .
so this will give the XOR function .To make it XNOR i need another NAND gate

so total number of NAND gates=2+4+3+1=10

but in my MCQ question it has only
a)3 b)4 c)5 d)6

i don't how to implement XNOR in one of above answers ,totally by NAND gates .can somebody help me ?
Thanks !

 

[overt26]

Three NAND gates can be combined to produce the double AND plus OR function. The rest are just those required for the invert operations.

 

[rclakmal]

ok thnaks !and i found some good ideas from wikepedia also !