Function that returns more than one variable in c

Question

I need to do a function that takes 3 floats and returns the average, the largest number among the 3 and the difference between the average and the largest. I tried to make the return by a pointer but one of the variables is not returned correctly and I can not find explanations on google, nor alternative ways to solve my problem. I know there must be other ways to do this program, but in the statement I have some restrictions: I cannot use global variables, including struct, the function parameters should be only 3 floats. What I wanted to know is what’s wrong in this program, why isn’t it working? Whether it’s about using the pointer or the logic is flawed...

//a comparação de valores não está correta
//o valor de mmd[1] não está sendo retornada corretamente

float *func_mmd(float a, float b, float c)//func_media_maior_diferenca
{
    float mmd[3];

    mmd[0]=(a+b+c)/3;//media

    mmd[1]=a;
    if(a>b || a>c)//comparação maior numero
    {
        mmd[1]=a;
    }
    else
        if(b>c || b>a)
        {
            mmd[1]=b;
        }
        else
            if(a==b && a==c && b==c)
            {
                mmd[1]=a;
            }
            else
            {mmd[1]=c;}


    mmd[2]=mmd[0]-mmd[1];//diferença

    printf("%f",mmd[1]);//este printf é só pra eu saber o que está sendo armazenada na variavel que calcula  o maior numero
    return (mmd);
}

int main()
{
    float a,b,c,*mmd;

    scanf("%f",&a);
    scanf("%f",&b);
    scanf("%f",&c);

    mmd=func_mmd(a,b,c);
    printf("\nA media eh:%f",mmd[0]);
    printf("\nO maior valor eh: %f",mmd[1]);
    printf("\nA diferenca entre a media e o maior numero eh: %f",mmd[2]);

    return 0;
}