What is the magnetic dipole moment of the given loop?

The magnetic moment of a current (i) carrying circular coil of radius (r) and number of turns (n) varies as :

(1) $1/r^2$                            

(2) $1/r$

(3) r                                  

(4) $r^2$

A small coil of N turns has an effective area A and carries a current I. It is suspended in a horizontal magnetic field $\stackrel{.}{B}$ such that its plane is perpendicular to $\stackrel{.}{B}$. The work done in rotating it by $180°$ about the vertical axis is 

(a) $NAIB$                               (b) $2NAIB$ 

(c) $2\mathrm{\pi NAIB}$                          (d) $4\mathrm{\pi }NAIB$

An electron moves with a constant speed v along a circle of radius r. Its magnetic moment will be (e is the electron's charge)

(1) evr                       

(2) $\frac{1}{2}$evr 

(3) ${\mathrm{\pi r}}^2$ev                    

(4) 2$\mathrm{\pi }$rev