A Charge of +3 $\mu$ C Is Distributed Uniformly Along the Circumference of a Circle

A charge of +3.0 $\mu$ C is distributed uniformly along the circumference of a circle with a radius of 20 cm.How much external energy is required to bring a charge of 25 $\mu$ C from infinity to the centre of the circle?

A) 5.4 J
B) 3.4 J
C) 4.3 J
D) 2.7 J
E) 6.8 J