A charged nonconducting rod, with a length of 2.81 m and a cross-sectional area of 2.24 cm², lies along the positive side of an x axis with one end at the origin. The volume charge density is charge per unit volume in coulombs per cubic meter. How many excess electrons are on the rod if is (a) uniform, with a value of -2.08 C/m³, and (b) nonuniform, with a value given by = bx², where b = -2.14 C/m⁵?