Solve the following linear programming problem graphically:
Maximise $Z = 4x + y$......$(1)$
subject to the constraints:
${x + y \leqslant 50}$.......$(2)$
${3x + y \leqslant 90}$......$(3)$
${x \geqslant 0, y \geqslant 0}$......$(4)$

In order to supplement daily diet,a person wishes to take some $X$ and some $Y$ tablets. The contents of iron,calcium and vitamins in $X$ and $Y$ (in milligrams per tablet) are given as below:

Tablets	Iron	Calcium	Vitamin
$X$	$6$	$3$	$2$
$Y$	$2$	$3$	$4$

The person needs at least $18$ milligrams of iron,$21$ milligrams of calcium and $16$ milligrams of vitamins. The price of each tablet of $X$ and $Y$ is $Rs. 2$ and $Rs. 1$ respectively. How many tablets of each should the person take in order to satisfy the above requirement at the minimum cost?

The difference between the maximum value and the minimum value of the objective function $z = 3x + y$ subject to the constraints $2x + 3y \leq 6$, $x + y \geq 1$, $x \geq 0$, $y \geq 0$ is....

The maximum value of $z=x+y$,subjected to $x+y \leq 10, 5x+3y \geq 15, x \leq 6, x, y \geq 0$,

The difference between the maximum value and minimum value of the objective function $z = 3x + 5y$ of a linear programming problem subject to constraints $5x + 10y \leq 50$, $x + y \geq 1$, $y \leq 4$ and $x \geq 0, y \geq 0$ is $3\lambda$. Then the value of $\lambda$ is

If the feasible region is as shown in the figure,then the related inequalities are: