What is the number of molecules of c2h5oh in a 3m solution that contains 4.00kg h2o?

The number of C2H5OH in a 3 m solution that contain 4.00kg H2O is calculate as below

M = moles of the solute/Kg of water

that is 3M = moles of solute / 4 Kg

multiply both side by 4

moles of the solute is therefore = 12 moles

by use of Avogadro law constant

1 mole = 6.02 x10^23 molecules

what about 12 moles

=12 moles/1 moles x 6.02 x10^23 = 7.224 x10^24 molecules