(37 # _ )
/ \
/ \
/ \
(21 # 29) (50 # _ )
/ | \ / \
/ | \ / \
(7,9,11) (21,23) (29,30) (37,49) (50,100)
Write the trace for 30 and 48.a) 37,21,29,29,30, successful
b) 37,50,37,49, unsuccessful