The owner of an ice cream shop is making signs to advertise. Each sign will be in the shape of a triangle to represent an ice cream cone. The sides of the triangle measure 17 cm 17 cm​​, and 16 cm The height from the shortest side to the opposite vertex is 15 cm. What is the area of one​ sign? How much material does the owner need to make 7 dozen​ signs?  ​