solve the integer knapsack problem with branch and bound algorithm by hand: max $10$x$1+12$x$2+7$x$3+1\mathrm{.}5$x$4$ subject to: $4$x$1+5$x$2+3$x$3+$ x$4<=10$ and x$1,$x$2$ belongs to positive integers, x$3,$x$4$ belongs to $0$ or $1$