Determine an expression for the loaded base overdrive factor

Question

For the loaded base overdrive factor determine an expression, σ_L of the transistor within the inverter circuit demonstrated below in terms of the circuit parameters. So, write the expression within terms of the unloaded overdrive factor of it, σ_U, (along with only the resistor R_C within the collector circuit). Estimate the value of R_L that will just bring the transistor to the edge of saturation while the input voltage is high at V_i = V_CC, when V_CC =5V, R_B = 10kΩ and R_C = 1k? as well as β_F = 40.