The below two C codes gives two different outputs, can someone explain why?

Question

The first code is :

#include <stdio.h>
int main() {
   int a,b,c;
   a = 4;
   b = ++a;
   c = b + a++;
   printf("%d",c);
   return 0;
}

Output is 10

The second code is :

#include <stdio.h>
int main() {
   int a,b;
   a = 4;
   b = ++a + a++;
   printf("%d",b);
   return 0;
}

The output is 11

The two codes should give 10 as the output I believe. Am I doing anything wrong? Can someone explain the above two scenarios?