$8.$

You are charged with maintaining a large C program, and you come across the following code:

$```$

typedef struct $\{$

int first;

a$\_$struct a$[$CNT$]$;

int last;

$\}$ b$\_$struct;

void test $($long i$,$ b$\_$struct $*$bp$)$

$\{$

int n $=$ bp$->$first $+$ bp$->$last;

a$\_$struct $*$ap $=$ &bp$->$a$[$i$]$;

ap$->$x$[$ap$->$idx$]=$ n;

$\}$

$```$

The declarations of the compile$-$time constant CNT and the structure a$\_$struct are in a file for which you do not have the necessary access privilege. Fortunately, you have a copy of the $.$o version of code, which you are able to disassemble with the OBJDUMP program, yielding the following disassembly:

$```$

void test$($long i$,$ b$\_$struct $*$bp$)$

i in $\%$rdi, bp in $\%$rsi

$0000000000000000$ :

lc: c$3$

$```$

$0$: $8$b $8$e $20010000$ mov $0$x$1$C$0(\%$rsi$),\%$ecx

$6$: $030$e add $(\%$rsi$),\%$ecx

$8$: $488$d $04$ bf lea $(\%$rdi,$\%$rdi,$4),\%$rax

c: $488$d $04$ c$6$ lea $(\%$rsi,$\%$rax,$8),\%$rax

$10$: $488$b $5008$ mov $0$x$8(\%$rax$),\%$rdx

$14$:$4863$ c$9$ movslq $\%$ecx,$\%$rcx

$17$:$48894$c d$010$ mov $\%$rcx$,0$x$10(\%$rax, $\%$rdx$,8)$

retq

Using your reverse engineering skills, deduce the following:

A$.$ The value of CNT$.$

B$.$ The size of a$\_$struct and the size of b$\_$struct.

C$.$ A complete declaration of structure a$\_$struct. Assume that the only fields in this structure are idx and $\backslash ($ x $\backslash ),$ and that both of these contain signed values.