; This is not a trick question.
; This is a real math problem, so don't say that a bus has no legs - and don't worry about the bus driver!
; There are 7 girls in a bus.
; Each girl has 7 backpacks.
; In each backpack, there are 7 big cats.
; For every big cat there are 7 little cats.
; Question: How many legs are there in the bus?
(define (legs-in-bus girls backpacks big-cats little-cats)
(define (girls-legs)
(* 2 girls))
(define (cats-legs cats)
(* 4 cats))
(define (backpack-legs)
(+ (cats-legs big-cats) (cats-legs (* big-cats little-cats))))
(+ (girls-legs) (* girls backpacks (backpack-legs))))