Please provide work, steps, formula(s), etc. Thanks!

A news article reported that Bill Ackman, who runs Pershing Square Capital Management, recently proposed the following: ...the government could establish and fund investment accounts for every child born in America. The funds could be invested in zero-cost equity index funds, be prohibited from withdrawal until retirement, and could compound tax free for 65 years. At historical rates of equity returns of 8% per annum, a $6,750 at birth retirement account...would provide retirement assets of more than $1 million at age 65." 1. I disagree with Ackman and believe that equity returns of 8% per annum estimate is optimistic. Accordingly, exactly how much would a $6,750 investment yield after 65 years at an annual rate of return of 6%