Bell metal is an alloy of which of the following?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$: Size of $Bk^{3+}$ ion is less than $Np^{3+}$ ion.
Reason $R$: The above is a consequence of the lanthanoid contraction.
In the light of the above statements,choose the correct answer from the options given below:

$A$ spring $40\,mm$ long is stretched by the application of a force. If $10\,N$ force is required to stretch the spring through $1\,mm$,then work done in stretching the spring through $40\,mm$ is ............. $J$.

$A$ horizontal pipe of non-uniform cross-section allows water to flow through it with a velocity $1 \ m/s$ when pressure is $50 \ kPa$ at a point. If the velocity of flow has to be $2 \ m/s$ at some other point,the pressure at that point should be (in $kPa$)

The cubic equation whose roots are the squares of the roots of $x^3-2x^2+10x-8=0$ is

The correct order of $C-O$ bond length in $CO$,$CO_3^{2-}$,and $CO_2$ is: