Cherry Rhubarb Pie

2 cups chopped rhubarb
1 (21 ounce) can cherry pie filling
¾ cup white sugar
2½ teaspoons quick-cooking tapioca
1 recipe pastry for a 9 inch single crust pie
1 tablespoon white sugar

Combine the rhubarb, cherry pie filling, sugar, and tapioca in a large bowl. Let stand for 15 minutes.
 
Pour filling into unbaked pie shell, and cover with pie crust. Brush top with milk, and sprinkle on sugar.

Bake at 400° F for 40 to 45 minutes.