CONTENT: 
 xrun 	           -- runs four test games of Acquire 
 with-contract.rkt -- specifies whether contracts are imposed on interfaces 

INSTRUCTIONS: 

 1. edit with-contract.rkt as desired 
 2. $ raco make xrun 
    it confirms which version is being run 
 3. $ ./xrun 

TIMINGS: 

 with contracts: 
  cpu time: 45 real time: 49 gc time: 0

 without contracts: 
  cpu time: 16 real time: 17 gc time: 0

