d) We can extract the symbol a from the list (b (a c) d) using car and cdr by going through the following steps: (cdr(b(ac)d))=>((ac)d) (car(cdr(b(ac)d)))=>(ac) (car(car(cdr(b(ac)d))))=>a For each of the following lists, write the expression using car and cdr that extracts the symbol a: - (b a c d) - ((b d) (c a)) III. Procedures Scheme provides an elegant way of defining procedures based upon the lambda calculus introduced by the logician Alonzo Church. When doing these exercises, you may find it convenient to save the definitions of the procedures in a file. These procedures can then be used again. They can be entered into Scheme from a file in which they were saved either by using a transfer mechanism or by invoking a loading procedure. In some implementations of Scheme, this is done with (load "filename")