Exercise 3.34.  Louis Reasoner wants to build a squarer, a constraint 
device with two terminals such that the value of connector b on the 
second terminal will always be the square of the value a on the first 
terminal. He proposes the following simple device made from a 
multiplier:

(define (squarer a b)
  (multiplier a a b))

There is a serious flaw in this idea. Explain.

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If the a connector has a value, the squarer will act as intended.

However, if only the b connector has a value, the multiplier will be 
under-constrained and will not supply a value to the a connector.