How to write the function state_totalpop(state* headstate), which takes in a pointer to the head element of a linked list and returns the total population sum for all elements in the list.

current code:
#include
#include
#include
typedef struct state_struct {
char code[3]; //two letter code of this state
int pop; //population of this state
struct state_struct* next; //pointer to next state
} state;
//state constructor
void state_create(state* thisstate, char thiscode[3], int thispop, state* nextstate) {
strcpy(thisstate-> code, thiscode);
thisstate-> pop = thispop;
thisstate-> next = nextstate;
}
void state_add(state* headstate, char addcode[], int addpop){
state* newstate = (state*)malloc(sizeof(state));
state_create(newstate, addcode, addpop, null);
state* currstate = headstate;
while (currstate-> next ! = null){
currstate = currstate-> next;
}
currstate-> next = newstate;
}
//returns total population for all states in list beginnging with *headstate
int state_totalpop(state* headstate){
int total = 0;
char stcode[3];
int statepop=0;
state* poplist = null;
poplist = (state*)malloc(sizeof(state));
state_create(poplist, stcode, statepop, null);
file* myfile = null;
myfile = fopen("uspops. txt", "r");
while (! feof(myfile)) {
fscanf(myfile, "%s", stcode);
fscanf(myfile, "%d", & statepop);
}
}
fclose(myfile);
return total;
}