$\backslash$Pi $\_4$:$=($KeyGen$\_4,$Tag$\_4,$Verify$\_4)$ is defined as follows:

$$KeyGen$\_4$ is identical to $$KeyGen$\_1,$ and it outputs a key k$.$

$$Tag$\_4[$k$,($m$\_1,$ m$\_2)]$ first runs $$Tag$\_1($k$,$ m$\_1)$ and obtains $\backslash$sigma $\_1$ and it runs $$Tag$\_2($k$,$ m$\_2)$ and obtains $\backslash$sigma $\_2.$ The final tag is

$\backslash$sigma $\backslash$sigma $\_1\backslash$sigma $\_2.$

Is $\backslash$Pi $\_4$ a secure MAC? Briefly explain why.