I don't want the answer. I want to the process of mental math. You will be reported if answer shows otherwise. Whoever answers may possibly get depending on depth of answer.

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3

a corroding iron, if that's one of your choices