고체역학 (Beer) — Pure Bending: Problem 4.197

4.197 The vertical portion of the press shown consists of a rectangular tube of wall thickness $t = 10 \text{ mm}$. Knowing that the press has been tightened on wooden planks being glued together until $P = 20 \text{ kN}$, determine the stress at (a) point $A$, (b) point $B$.