This is his solution.
The minimum is Vam=-66.67
min
min(,,)
1
ambmcm
aam
bbm
ccm
vvvv
vv
vvv
=
éùéù
éù
êúêú
êú
=-
ëû
ëûëû
66.67
min(,,)66.67
-
==-
=--=
91.07
24.4
--=
10
2
0.50.866
3
am
bm
cm
v
a
b
--