Reword the “Worth of Substances” rule to:-

Each Substance has a Minimum Worth between $1 and $5 per tonne and a Maximum Worth between the Minimum Worth and $8 per tonne; these are tracked privately by the Traffic Warden. Each substance may also have a Market Value per tonne, also measured in $, and which may be different for each Moon. Market Value is tracked in the table below. If no Market Value is specified for a substance on a particular Moon, it has no Market Value there.

As a weekly action, for each Substance and each Moon, the Traffic Warden should privately choose a random number between that Substance’s Minimum Worth and Maximum Worth, inclusive, to be that Substance’s Market Value in $ for that Moon. (The Market Value of Iron is not chosen randomly and is instead always $1.) The Traffic Warden shall then update the table below to reflect the current Market Value.

{| class="wikitable"
|-
|
!Iron
!Ice
!Sulphur
|-
!Io
|1
|9
|8
|-
!Europa
|1
|11
|9
|-
!Ganymede
|1
|9
|11
|-
!Callisto
|1
|9
|13
|-
|}