A 0.350-m-long cylindrical capacitor consists of a solid conducting core with a radius of 1.20 mm and an outer hollow conducting tube with an inner radius of 2.00 mm. The two conductors are separated by air and charged to a potential difference of 6.00 V. Calculate
(a) the charge per length for the capacitor;
(b) the total charge on the capacitor;
(c) the capacitance;
(d) the energy stored in the capacitor when fully charged.