The diagram shows three aid stations in a national park. choose the values of x, y, and z that could represent the distances between the stations.
a) x = 7 miles, y = 8 miles, z = 18 miles
b) x = 4 miles, y = 7 miles, z = 12 miles
c) x = 5 miles, y = 9 miles, z = 14 miles
d) x = 8 miles, y = 12 miles, z = 15 miles