Question $1(40$ pts$)$

$1\mathrm{.}1.$ On the following diagram of the Diffie$-$Hellman key exchange, clearly indicate which of the following

six values are public and which are private $(20$ pts$)$:

$a,b,g,p,g^a$modp,$g^b$modp

$1\mathrm{.}2.$ What is the symmetric key that Alice and Bob agree on$?(20$ pts$)$