What is the problem with the following code snippet?

double discount(double& cost)

{

 return (0.9 * cost);

}

int main ()

{

 cout << discount(49.95);

}

a.

The data type returned by the function discount does not match the return type.

b.

The argument to the function discount must be a variable.

c.

The function discount must return void.

d.

The code is correct.

Clear my choice