B-80 & the Ship's Code Card vs the Nav Gen answers

Hi Folks,
Studying Nav Gen at the moment and can not make these questions work out. As an example:
3 USCG #1019
You are preparing a weather report form, WS Form B-
80. The dry bulb thermometer reads 30°F (-1°), and
the wet bulb thermometer reads 28°F (-2°C). Using the
Ships Code Card, how would you encode the air
temperature groups in the report?

10011, 2003/

11300, 2124/

11011, 2124/

[B]11011, 2104/ [/B]the USCG answer…


Using the Ship’s Card I get 11010, 81020 or if you make an assumption that the bulb is frozen (which is not stated in the question) 81020 becomes 82020…

Any in site would be appreciated!!