Modelling Exercise Using Labelled Transition Systems

Define an LTS describing the behaviour of a vending machine that obeys the following constraints.

• The vending maching can dispense coffee, tea and chocolate.
  
• Coffee costs 20 cents, tea costs 10 cents and chocolate costs 20 cents.
  
• The machine accepts 10 and 20 cent coins.
  
• The machine never makes a profit and does not give change.
  

Try not to impose other restrictions on the behaviour of the vending machine.