The language is R5RS.

[3 marks] Observe that Scheme's model of evaluation allows for combinations where the operator is itself a combination. Use this observation to describe the behaviour of the following procedure: (define (foo a b) ((cond (> b 0) + ((= b 0) *) (else ))) a b)) Your answer should describe what happens for all integer values of a and b. Illustrate your answer using the substitution model