Question from the Language C - Fundamentals test

In C, knowing that on the machine where the following code is executed a long weighs 8 bytes, a char 1 byte and a short 2 bytes, give the size in bytes of the following structure (1 correct answer only) :

struct t {
 long z;
 union U {
    long a;
    char b;
    long c;
 }u;
};