$($a$)$ Suppose that Bob observes two consecutive signed messages, say $($xi$,$ sig$($xi$))$ and $($xi$+1,$ sig$($xi$+1)).$ Describe how Bob can easily compute Alice's secret key, a$,$ given this informationm, without solving an instance of the Discrete Logarithm problem. $($Note that the value of i does not have to be known forthe attack to succeed.$)$

$($b$)$ Suppose that the parameters of the scheme are $p=28703,=5$ and

$=11339,$ and the two messages observed by Bob are

$x_i=12000,$sig$(x_i)=(26530,19862)$

$x_{i+1}=24567,$sig$(x_{i+1})=(3081,7604).$

Find the value of a using the attack you described in part $($a$).$