mapproject problem 2D coordinate transformation

Dear list,
This is my very first message since I'm using GMT only from a few months.
The version I've installed is the  4.5.9 (the one I downloaded from the
repository with synaptic).
The issue I'm struggling with is the following: I need to get new
geographic coordinates of a rectangular area (so just 4 vertices) from
linear ones, so that I could plot this rectangular box, in a second moment
using psxy, over a pscoast map generated with the same projection.
My file coordinate (COORD) in inputs are:
0 0
0 30
40 30
40 0

...and the command line is the following:

mapproject COORD -R10.65/43.05/11.50/43.45r -Jt10.65/43.05/1:1000000 -Fk -I
-V > lonlat_coord

results:
-349.35    43.0500000009
-349.35    43.3200358947
-348.856890988    43.3189729577
-348.859059585    43.0489469894
-349.35    43.0500000009

So...this is odd... but the standard output says:

mapproject:  Transform 10.55/11.6/42.9468847402/43.5531591954 <-
0/174757.13088/0/113766.688743 [km]
mapproject: Working on file COORD
mapproject: Projected 5 points
mapproject: Input extreme values:  Xmin: 0 Xmax: 40 Ymin: 0 Ymax 30
mapproject: Output extreme values:  Xmin: 10.65 Xmax: 11.1431090123 Ymin:
43.0489469894 Ymax: 43.3200358947
mapproject: Mapped 5 x-y pairs [km] to lon-lat

The result I want is a combination of the coordinates in the second-last
line..but I can't in any way put them on the output file..
I read the documentation and searched troubleshooting  for this case...but
nothing seems to resolve it. Where I'm going wrong?

I'd really appreciate any type of help.
Have a nice day

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