What was the six$-$month GMROI for a department that had gross margin of $$480,000$ and monthly stocks $($at cost value$)$ as follows for the $6-$month period ending January $31?$

August $1$ $ $90,000$

September $1$ $ $100,000$

October $1$ $ $115,000$

November $1$ $ $185,000$

December $1$ $ $285,000$

January $1$ $ $125,000$

February $1$ $ $90,000$