Consider the following linear programming model. maximize Z $20$x$130$x$210$x$340$x$4$ C$-14$ subject to $2$x$14$x$23$x$37$x$4?1010$x$17$x$220$x$315$x$4?40$ x$110$x$2$ x$3?10$ x$1,$ x$2,$ x$3,$ x$4=0$ or $1$ a$.$ Solve this problem using the implicit enumeration method. b$.$ What difficulties would be encountered with the implicit enumeration method if this problem were expanded to contain five or more variables and more constraints?