Henderson Office Supply is considering a more liberal credit policy to increase sales but expects that $10$ percent of the new accounts will be uncollectible. Collection costs are $5$ percent of new sales, production and selling costs are $79$ percent, and accounts receivable turnover is five times. Assume income taxes of $30$ percent and an increase in sales of $\backslash (\backslash$$ $84,000\backslash ).$ No other asset buildup will be required to service the new accounts. a$.$ What additional investment in accounts receivable is needed to support this sales expansion? b$.$ What would be Henderson's incremental aftertax return on investment? $($Input your answer as a percent rounded to $2$ decimal places.$)$