Both Neptune and Pluto travel around the sun in elliptical orbits. For Neptune's orbit, a = 30.10, and for Pluto's orbit, a = 39.44, where the variable a represents their average distances from the sun in astronomical units. (One astronomical unit equals 93 million miles.) The value of the variable a also corresponds to half the length of the major axis. Pluto has a highly eccentric orbit with e = 0.249, and Neptune has a nearly circular orbit with e = 0.009.

Calculate the value of c for Neptune and Pluto.