(7) [5 points] The resistivity of materials may be controlled by doping them with variable amounts of impurities. Consider a strip of ohmic material with cross sectional area A and length L, with voltage V applied across the ends of the strip. The resistivity varies along the position in x on the strip as p(x) = Pox/x0. (a) Find the total resistance of the strip. Hint: consider the resistance of a thin slice in x of the strip and integrate. (b) The current and current density must be the same at all points along the strip (since neither charge nor current may be created or destroyed). Use this idea and Ohm's Law to find the electric field at position x along the strip