Calculate the Capacitance Between Two Concentric Spheres

The simple electromagnetism calculator which is used to calculate the capacitance between the two concentric spheres. The surface of a sphere having radius r1 and radius r2 which carries a charge.
Formula: C = 4π εoεrab(b-a)-1
Where, C = Capacitance of Concentric Spheres, a,b = Radius, εo = Permittivity of Free Space, εr = Relative Permittivity
Permittivity of Free Space (εo): Radius(A): 
Relative Permittivity (εr): Radius(B):
Capacitance of Concentric Spheres: F