understanding bandwidth usage calculation, on streamyx

Broadband provider
ISP/package: STreamyx 4MB
Location: Ampang
Have you called your ISP's helpline?: No

Personal equipment
Modem: Dlink DSL 2640B
Router:
Firewall used: None

Hi,

I just want to have better understanding on the bandwidth usage calculation.

Let say I have a 4MB streamyx connection, and I am sharing with 3 other user using network cable. I am heavy on internet browsing, another is heavy on online gaming, while the other 2 user is heavy on youtube.

What is the bandwidth usage calculation going to be? Please advise thank you.