Viski Vemmelsri specializes in triple jumping. In this sport, the overall performance is divided into three parts, a leap, a step and a jump. In the measurements carried out during the season, it was found that the parts of Viski Vemmelsri's performances follow a normal distribution approximately as follows: Leap ~ (5.6, 0.42), Step ~ (5.0, 0.72) and jump ~ (6.1, 0.82).

Let's assume that the parts of the jump are independent of each other. What is the proportion of triple jump performances whose total length exceeds 18 meters?