Timothy has begun selling copies of his first work of art. In the first year, he sold 200 copies. In the second year, he sold 240 copies. In the sixth year, he sold 400 copies. Suppose that he continues to increase his sales at the same rate.

Write an equation that will help Timothy calculate how many copies of his work he can expect to sell each year after y years.

Instruction : Do not simplify the expression. Use opening brackets ( and closing brackets) where needed. Start your answer with N=. Write your answer without any space(s).