$--$In a paragraph or less define the rule of $72$ as it applies to finance$/$investing$.--$At $20$ years old, assume you have $$50,000$ of post$-$tax lottery winnings of which you invest in a diversified portfolio of stocks that will earn an annual return of $10\%.$ How long will it take for you to double your money?$--$At age $62,$ approximately how much money will you have, assuming the rule of $72$ is in effect?