Select the correct passive voice of the given sentence.
Rajeshwari helped her mother to bake a cake.
1
Her mother was helped by Rajeshwari to bake a cake.
2
Her mother is helping by Rajeshwari to bake a cake.
3
Her mother has helped Rajeshwari to bake a cake.
4
Her mother had helped by Rajeshwari to bake a cake.