In orthorhombic, the value of a, b and c are respectively

4.2 Å 8.6 Å and 8.3 Å given the molecular mass of the solute is 155 g mol ^-1 and that of density is 3.3 g/ cc, the number of formula units per unit cell is

a. 2

b. 3

c. 4

d. 6

Ans. c