Your grandfather started his own business 52 years ago. He opened an investment account at the end of his third month of business and contributed $x. Every three months since then, he faithfully saved...

Your grandfather started his own business 52 years ago. He opened an investment account at the end of his third month of business and contributed $x. Every three months since then, he faithfully saved another $x. His savings account has earned an average rate of 5.73 percent annually. Today, his account is valued at $289.209.11. How much did your grandfather save every three months assuming he saved the same amount each time?

Can the calculator and excel solution be provided?