Answer:
struggle for brightness
Step-by-step explanation:
From the excerpt, we can see that the atmosphere was dull and there there was no sales. He has sat in his office for over six hours and no customer has patronized him.
It was like there was a struggle for him. The event around his lack of sales was discouraging and depressing.
Somber mood talks of a mood that is depressing and sad due to certain circumstances.