In a phrase where the subject is "mass of people", should I use "its"?
e.g.
A mass of people and its flag.
Mass is an abstract word, so it sounds strange to me to use their; but I'm not sure.
EDIT:
Seems that according notional agreement I should use their
but
If the mass of people act like a cohesive body, e.g.
a mass of people is/are united in its/their flag
Is this a situational agreement and is the use of plural forms wrong?
Could you help me?