Q56. A spherical shell of outer radius R and inner radius R/2 contains a solid sphere of radius R/2 (see figure). The density of the material of the solid sphere is ρ and that of the shell is ρ/2. What is the average mass density of the larger sphere thus formed?
(a)3ρ/4
(b)9ρ/16
(c)7ρ/8
(d)5ρ/8