For Part A
The energy density at r=11.1 cm just outside the inner sphere, is 25.9 J/m3
For Part B
The energy density at r=14.9 cm, just inside the outer sphere, is 24.1 J/m3
Both of these energy densities are determined using the formula for the potential energy of a charged object
U=qV
Where q is the charge, and V is the voltage, to get this energy density in joules per meter cubed we then divide by the volume