The country gains or loses as area LGW is larger or smaller than area
RSWV.
The effect on joint welfare of A and V is also ambiguous. They benefit jointly if area LGV is larger than area HSU, but lose otherwise.
Conclusion: the union as a whole loses from the FTA.
The higher the initial tariff, the larger the favorable effect (area LUG) and smaller the unfavorable effect (area USH).
The lower the post-FTA tariff on extra-union countries, the less likely that the lower-price goods of the latter will be displaced.