The description does not say that heptagon has to be convex, i.e. all of its interior angles need not be less than ${180}^{\circ }$. Since $(2x7-4)\times 90=900$, the interior angles of all heptagons total ${900}^{\circ }$. The creation of a heptagon with all the given conditions is possible as the diagram shows. Notice that four of the interior angles are acute and the other three are reflex angles.