Suppose that two parties A and B wish to set up a common secret key $($D$-$H key$)$ between themselves using the Diffie Hellman key exchange technique. They agree on $7$ as the modulus and $3$ as the primitive root. Party A chooses $2$ and party B chooses $5$ as their respective secrets$.$ Their D$-$H key is$-----$

Select one:

a$.5$

b$.3$

c$.4$

d$.2$