Many roller coasters have loops where carts roll on a track that curves sharply up into the air. At the top, the people are upside down (and usually screaming). For safety reasons, many of these roller coasters must have a minimum speed at the top of the loop. In the roller coaster shown in the figure, the cart must have a minimum speed of 10.0 m/s at the top of the loop to make it around safely. Assuming that the roller coaster starts from rest at the top of the first hill and there is no friction on the roller coaster, what is the minimum height of the first hill?