Message Authentication Codes

$(10$ pt$.)$ Consider the following message authentication code that on input a message $m,$

produces a tag for the message as follows

$t(m)=F_{}(m)||F_{}(mo+r)$

where $F$ is a PRF that is known to be secure$,r$ is fixed and known to the adversary,

and $||$ is appending $F_{}(mo+r)$ to $F_{}(m).$ Do you think this is a secure MAC? If not, what

property is this construction violating? Can you show an example where this property is

being violated?