Chemistry the mole concept

hi can u please help me with this question.
in 4 moles of Na2CO3
calculate the mass ( in grams) of CO3 ions

In 1 mole of Na2CO3 the mass of CO3 is calculated as follows:
Mr (CO3) = 12 + (16 * 3)
= 60g
In 4 moles of Na2CO3 the mass of CO3 is calculated as follows:
Mr 4(CO3) = 4 * (12 + (16 * 3))
= 240g