A charged nonconducting rod, with a length of 1 m and a cross-sectional area of 4 cm, lies along the positive side of an x axis with one end at the origin. The volume charge density p is the charge per unit volume in coulombs per cubic meter. How many excess electrons are on the rod if p is (a) uniform, with a value of -4 C/m; (5 marks) (b) nonuniform, with a value given by p = exp(-x) C/m. (5 marks)