4. Consider a pure silicon crystal uniformly doped with 5x(10's) boron atoms/cm3. What is the doping type (n or p)? If the lattice scattering contribution to carrier mobilities has the explicit absolute temperature dependence: 300 V Hz = 300 I where v equals exactly 1.5 and Uzoo is 480 cm?/volt sec for holes and 1400 cm/volt sec for electrons and if the ionized impurity contribution to carrier mobilities has the explicit absolute temperature dependence: OL T /2 300 where a=2.0x(10") per cm volt sec for holes and 4.5x(10") per cm volt sec for electrons and C, is the total ionized impurity concentration, what, then is the resistivity of the silicon crystal at -73 C, 27C, and 127C? If an additional 2.5x(1017) boron atoms/cm3 and 2.5(10') phosphorus atoms/cm3 together are uniformly added to the crystal, what happens to carrier concentrations, mobilities, and resistivities at the three temperatures