Howard has just been hired and asked to complete his retirement benefits package. His company is willing to meet his end of the year contributions (e.g. if Howard decides to invest 5% of his salary at the end of every year into his retirement fund, his employer contributes with additional 5%, hence Howard's retirement plan is financed with an annual amount equal to 10% of his salary) and the retirement fund guarantees an annual yield of 5%. For simplicity purposes assume that Howard will have the same annual salary of 139,968 dollars for the next 29 years and then retires (assume that there is nothing else to consider, e.g. taxes). If Howard's goal is to have $4 million upon retirement, which PERCENTAGE of his income should he save every year?