text(Molarity) = text(Weight of solute)/text(Gram molecular weight of solute) xx 1000 / (text(Volume of solution in ml))
text(Molarity) = text(Weight of NaOH)/text(Gram molecular weight of NaOH) xx 1000 / (text(Volume of solution in ml))
text(Molarity) = 4/40 xx 1000/(250)
text(Molarity) = 0.4 text(M)