Let E$17(0,7)$ be an elliptic curve defined over Z$17.$ Assume two people A and B want to exchange a secret key using Elliptic Curve Diffie$-$Hellman Key Exchange $($ECDH$)$ method. Given the primitive element $($generator$)$ G $=(15,13),$ the two private key nA$=3$ and nB$=5,$ please calculate the secret key K$.$

a$.(6,6)$

b$.(8,14)$

c$.(8,3)$

d$.15$