Find the built-in potential for a p-n si junction at room

Question

1. Find the built-in potential for a p-n Si junction at room temperature if the bulk resistivity of Si is 1Ωcm. Electron mobility in Si at RT is 1400 cm² V^-1 s^-1; μ_n/μ_p = 3.1; n_i;= 1.05 x 10¹³ cm^-3.

2. For the p-n Si junction from the previous problem calculate the width of the space charge region for the applied voltages V = -10, 0, and +0.3 V. ∈_si = 11.9