Guys, help me solve these problems. i'm really in big trouble.. thanks guys!

a)Two charges of equal magnitude exert an attractive force of 4.0x10-4 N on each other. If the magnitude of each charge is 2.0μC, how far apart are the charge?

b)Three equal charges, each of +6.0μC, are spaced along a line. The end charges are each 0.23 m from the central charge. What are the magnitude and direction of the force on each charge?

c)Two small, positively charged spheres experience a mutual repulsive force of 1.52 N when their centers are 0.200 m apart. The sum of the charges on the two spheres is 6.00μC. What is the charge on each sphere?

d)Four equal point charges +q are placed at the corners of a square of edge length L. Find the force on any one of the charges.

e)Two equally charged insulating balls each weigh 0.10g and hang from a common point by identical threads 30cm long. The balls repel each other so that the separation between their center is 6.4 cm. What is the magnitude of the charge on each ball?