If, in Prob. 13, the axes are grounded (u = 0), what constant potential must the other portion of the boundary have in order to produce 220 V at P₁₁?

Data from Prob. 13

Solve the mixed boundary value problem for the Laplace equation ˆ‡²u = 0 in the rectangle in Fig. 458a (using the grid in Fig. 458b) and the boundary conditions u_x = 0 on the left edge, u_x = 3 on the right edge, u = x² on the lower edge, and u = x² - 1 on the upper edge.

%3D 0 -- 1.5 2 3 %3 P. 12 22 %3D 0- - - - 9- P Pa 11 21 1. 2 x 3.