A Planet Is Made of Two Distinct Materials in Two

A planet is made of two distinct materials in two layers. From the core to R/2, the density of the material is 4000 kg/m³, and from R/2 to R the density is 3000 kg/m³. What is the mass of the planet if R = 5000 km?

A) 2.62 * 10²³ kg
B) 1.37 * 10²⁴ kg
C) 1.64 * 10²⁴ kg
D) 1.57 * 10²⁴ kg
E) 1.87 * 10²⁴ kg