Pollen: Change table ids to a and b

psGrammar/challenge/pollen/challenge.jsgf

@@ -3,7 +3,8 @@ grammar pollen;
 public <orderstring> = [<robot>] (<receiveorderstring> | <tablestring>);
 
 <receiveorderstring> = bring [me] [a] <drink>;
-<tablestring> = [table] <number>;
+<tablestring> = table <table>;
+<table> = (a | b)
 
 <drink> = (tea | coke | fanta | water);
 <number> = (one | two | three | four | five | six | seven | eight | nine | zero);