Sift flour, baking powder and salt, add sugar. Cut in margarine
as for a pie crust. Break egg into measuring cup then add
enough milk to make 1 cup. Add to dry ingredients. Mix well
and put into greased 10 X 15 X 1 inch pan. Cover with the pie
filling. Mix topping flour, sugar and margarine, crumble over
pie filling. Bake at 350 degrees for 30 to 35 minutes. Mix
powder sugar and milk to make a frosting and drizzle thin layer
over top of coffee cake.