Vinegar Pie
["1 c. sugar", "2 1/2 Tbsp. flour", "1 c. cold water", "5 Tbsp. vinegar", "4 eggs (reserve 2 whites for meringue)", "2 Tbsp. margarine", "1 tsp. vanilla", "1 (9-inch) baked pie shell"]
["A little more sugar may be needed."]
["sugar", "flour", "cold water", "vinegar", "eggs", "margarine", "vanilla", "shell"]