Which of the following functions is not linear? Oz $5$x $+3$Z O $3$X $+4$YZ$-3$ O $2$x $+5$YZ QUESTION $19$ Which of the following is not a part of every linear programming problem formulation? non$-$negativity constraints a set of constraints O a redundant constraint O an objective function QUESTION $20$ Which of the following is not acceptable as a constraint in a linear programming problem $($maximization$)?$ Constraint $1$ X $+$ XY$+$Y$212$ Constraint $2$ X$-2$Y S $20$ Constraint $3$ X $3$Y $=48$ Constraint $4$ X$+$Y$+$Z $ $150$ Constraint $1$ O Constraint $2$ Constraint $3$ Constraint $4$ DO