The total cost (c) is proportional to the number of pineapples (n) purchased. The price of each pineapple is $4. Which equation represents the total cost of the pineapples purchased?

The pyraminx is a rubik's cube-type toy in the shape of a tetrahedron. the pyraminx shown below has edges 15\,\text{cm}15cm long and vertical height h=12.2\,\text{cm}h=12.2cm. the triangle drawn with dashed lines is a right triangle. what is the distance rr? round your answer to the nearest tenth.