(item "Green LEDs"
2 .1 1 "evil mad science?")
(item "330 Ohm Resistors"
- 6 .1 1 "evil mad science?")))
+ 6 .1 1 "evil mad science?")
+ (item "motor controller"
+ 1 (/ 5.2 5) 10 (string-append "http://www.ebay.com/"
+ "itm/like/180976411359?lpid=82"))))
(define total-cost
(apply + (for/list ([thing bill-of-materials])