Convert 1.72 moles of magnesium carbonate to formula units

One mole any substance contains 6.022 ₓ 10²³ particles called Avogadro's Number.

The relation between moles and number of particles is given as,

                        # of particles  =  moles ₓ Avogadro's number

In our case the particles are formula units of MgCO₃. So, 1 mole of MgCO₃ contain 6.022 ₓ 10²³ formula units, then the number of formula units in 1.72 moles are calculated as,

              # of formula units  =  1.72 mol ₓ 6.022 ₓ 10²³ formula units / mol
            
             # of formula units   =  1.035 ₓ 10²⁴ Formula Units

Sorry i think the answer is b