For extremal Kerr spacetimes, a = ±M, the innermost stable circular orbits for massive particles are respectively at r = M and r = 9M in Boyer-Lindquist coordinates. (Hartleplots this

in his Figure 15.3, but doesn't mention 9M in the text.) (a) For both of these cases, find e and l from Hartle's Equation (15.17). (b) For both of these cases, find dø/dt from Hartle's Equation (15.18).