I'm struggling with the following puzzle:

I have a group of friends of which 60% is male.
I have a group of colleagues of which 70% is male.

Someone I know is both a friend and a colleague.

What is the chance that this person is male?

a) < 60 %
b) 60 %
c) between 60 en 70%
d) 70%
e) > 70%

(and why?)

Thanks for your help!
- BigFurryMonster