Compare the number of nodes in the branch$-$and$-$bound tree with the following

naive brute$-$force enumeration approach: check each of the $24=16$ possible

values of x $=$

x$1$ x$2$ x$3$ x$4$

T

with xi in $\{0,1\},$ for i $=1,...,4,$ and pick the

best feasible solution among them.