(defun sum (the-list)
	(cond
		((null the-list)
			0
		)
		(T
			(+ (car the-list) (sum (cdr the-list)))
		)

	)
)


Demo: 

[9]> (sum ())
1. Trace: (SUM 'NIL)
1. Trace: SUM ==> 0
0
[10]> (sum '(496))
1. Trace: (SUM '(496))
2. Trace: (SUM 'NIL)
2. Trace: SUM ==> 0
1. Trace: SUM ==> 496
496
[11]> (sum '(1 11 111))
1. Trace: (SUM '(1 11 111))
2. Trace: (SUM '(11 111))
3. Trace: (SUM '(111))
4. Trace: (SUM 'NIL)
4. Trace: SUM ==> 0
3. Trace: SUM ==> 111
2. Trace: SUM ==> 122
1. Trace: SUM ==> 123
123
[12]> (sum '(1 2 3 4 5 6 7 8 9 10))
1. Trace: (SUM '(1 2 3 4 5 6 7 8 9 10))
2. Trace: (SUM '(2 3 4 5 6 7 8 9 10))
3. Trace: (SUM '(3 4 5 6 7 8 9 10))
4. Trace: (SUM '(4 5 6 7 8 9 10))
5. Trace: (SUM '(5 6 7 8 9 10))
6. Trace: (SUM '(6 7 8 9 10))
7. Trace: (SUM '(7 8 9 10))
8. Trace: (SUM '(8 9 10))
9. Trace: (SUM '(9 10))
10. Trace: (SUM '(10))
11. Trace: (SUM 'NIL)
11. Trace: SUM ==> 0
10. Trace: SUM ==> 10
9. Trace: SUM ==> 19
8. Trace: SUM ==> 27
7. Trace: SUM ==> 34
6. Trace: SUM ==> 40
5. Trace: SUM ==> 45
4. Trace: SUM ==> 49
3. Trace: SUM ==> 52
2. Trace: SUM ==> 54
1. Trace: SUM ==> 55
55


(defun product (the-list)
	(cond
		((null the-list)
			0
		)
		((= (length the-list) 1)
			(car the-list)
		)
		(T
			(* (car the-list) (product (cdr the-list)))
		)
	)
)


Demo:

[13]> (product ())
1. Trace: (PRODUCT 'NIL)
1. Trace: PRODUCT ==> 0
0
[14]> (product '(496))
1. Trace: (PRODUCT '(496))
1. Trace: PRODUCT ==> 496
496
[15]> (product '(1 11 111))
1. Trace: (PRODUCT '(1 11 111))
2. Trace: (PRODUCT '(11 111))
3. Trace: (PRODUCT '(111))
3. Trace: PRODUCT ==> 111
2. Trace: PRODUCT ==> 1221
1. Trace: PRODUCT ==> 1221
1221
[16]> (product '(1 2 3 4 5 6 7 8 9 10))
1. Trace: (PRODUCT '(1 2 3 4 5 6 7 8 9 10))
2. Trace: (PRODUCT '(2 3 4 5 6 7 8 9 10))
3. Trace: (PRODUCT '(3 4 5 6 7 8 9 10))
4. Trace: (PRODUCT '(4 5 6 7 8 9 10))
5. Trace: (PRODUCT '(5 6 7 8 9 10))
6. Trace: (PRODUCT '(6 7 8 9 10))
7. Trace: (PRODUCT '(7 8 9 10))
8. Trace: (PRODUCT '(8 9 10))
9. Trace: (PRODUCT '(9 10))
10. Trace: (PRODUCT '(10))
10. Trace: PRODUCT ==> 10
9. Trace: PRODUCT ==> 90
8. Trace: PRODUCT ==> 720
7. Trace: PRODUCT ==> 5040
6. Trace: PRODUCT ==> 30240
5. Trace: PRODUCT ==> 151200
4. Trace: PRODUCT ==> 604800
3. Trace: PRODUCT ==> 1814400
2. Trace: PRODUCT ==> 3628800
1. Trace: PRODUCT ==> 3628800
3628800