Find the error(s) in each of the following, and explain how to correct it (them):

a) ```
string string1( 28 ); // construct string1
string string2( 'z' ); // construct string2
```
b) ```
// assume std namespace is known
const char *ptr = name.data(); // name is "joe bob"
ptr[ 3 ] = '-';
cout << ptr << endl;
```

a) Constructors for class string do not exist for integer and character arguments. Other valid constructors should be used—converting the arguments to strings if need be.
b) Function data does not add a null terminator. Also, the code attempts to modify a const char. Replace all of the lines with the code:
cout << name.substr( 0, 3 ) + "-" + name.substr( 4 ) << endl;