2. (4 pt) (Varlang syntax and semantics, scoping] Compute the values of the following Varlang expressions (return an error if the values cannot be computed). Please list the steps to show that you understand the scoping rules and semantics of the VarLang program. Hint: section 3.5 of Rajan-PL book (a) (2 pt) (let ((a 0) (b 4)) (let ((a b)) (+ a b))) (b) (2 pt) (* (let ((b 4)) b) (let ((c 11) (a b)) (- a c))) 2. (4 pt) (Varlang syntax and semantics, scoping] Compute the values of the following Varlang expressions (return an error if the values cannot be computed). Please list the steps to show that you understand the scoping rules and semantics of the VarLang program. Hint: section 3.5 of Rajan-PL book (a) (2 pt) (let ((a 0) (b 4)) (let ((a b)) (+ a b))) (b) (2 pt) (* (let ((b 4)) b) (let ((c 11) (a b)) (- a c)))