Specific WAN IP per user group

RouterOS General
1

I have 500 pppoe clients and I have 5 WAN IPs from my provider
How do I set a different WAN IP for each 100 users?

Example:
4mb User group will use: 45.45.45.2
2mb User group will use: 45.45.45.3
etc

2 
/ip firewall nat
add chain=srcnat out-interface-list=WAN src-address-list=group1 action=srcnat to-address=45.45.45.2
add  chain=srcnat out-interface-list=WAN src-address-list=group2 action=srcnat to-address=45.45.45.3

And then disable/remove default masquerade rule.

3

Thank you for this, I will try implementing it