[Chemistry] Rate Law Mechanism Problem?

[talentedDavid]

The net equation is as follows:

A2B + 3 MX3 --> M3B + A2X2 + 3 X2

where A,B, X and M are elements. The experimentally proven rate law expression is as follows : R =k[MX3]^1

Asuuming the rate determining step for this reaction is step #2 of a four step mechanism is as follows:

A2B + MX3 --> A2X2 + MBX
.....propose a possible 4 step mechanism that inolves 1 to 1 collisions.

i keep trying and yet im not getting steps number 3 and 4. HELP someone

please show ALL steps!!
(please and thank you)