Kindly help me out in this question,

1. A tin nucleus has charge +50e.If the proton is at 10^-12 m from the nucleus,then the potential at this position,is (charge on proton is 1.6 x 10^-19)

Electrostatics question based on earthing of spherical shell

an object has a charge of 2c and gains 10^19 electrons. the net chaarge on the object becomes??

A wire with a linear charge density lambda forms a quarter of a cjrclenof radius R and is placed asa shown in thefigure with its centre of curvature at the origin O the electric field at O will be

Find the value of q so that system remains in equilibrium.. figure attached below

Find the value of q so that system remains in equilibrium