Mix margarine and sugar, then add egg and then dry ingredients. Divide in three and press into greased pie dishes. Prick bases then bake at 180 C for 10 - 15 minutes, or till golden brown. Cool. Mix condensed milk to yolks. Place in pastry shells. Whip whites, water and salt. Beat in sugar. Spread over bases, being sure to seal well. Bake at 180 C for 8 - 10 minutes, till golden and whites have cooked.