5.3.1.14 Construction of secrets

Condition: on the ribs \ (a c, b c \) and \ (c c_ {1} \) prisms \ (a b c a_ {1} b_ {1} c_ {1} \) the points \ (q, r \) and \ (s \) are set respectively. Build a section of the prism with a plane parallel plane \ (q r s \) and passing through a point \ (p \) set on the edge \ (b_ {1} \).