Oxidation number of $P$ in $Mg_2P_2O_7$ is

In $YDSE$,the separation between the slits is halved and the distance between the slit and the screen is doubled. The fringe width is

Observe the statements given below :
Assertion $(A)$ : $f(x)=x e^{-x}$ has the maximum at $x=1$
Reason $(R)$ : $f^{\prime}(1)=0$ and $f^{\prime \prime}(1) < 0$
Which of the following is correct?

At $25 \ ^\circ C,$ the solubility product of $Mg(OH)_2$ is $1.0 \times 10^{-11}.$ At which $pH$ will $Mg^{2+}$ ions start precipitating in the form of $Mg(OH)_2$ from a solution of $0.001 \ M \ Mg^{2+}$ ions?

The area (in square units) of the region bounded by the curves $x=y^2$ and $x=3-2y^2$ is