You are considering using trade credit as a way of reducing your working capital needs. You currently receive a $2\%$ discount because you pay in $30$ days, but you could give up the discount and pay in $90$ days.You purchase $$100$ million worth of supplies $($before the $2\%$ discount$)$ every year, and your cost of capitalis $10\%.($Tax rate $=40\%.)$a$.$ Estimate the increase in accounts payable, if you go to the $90-$day payment period from a $30-$day payment period.b$.$ With your current cost of capital, will using trade credit increase or decrease value? $($You can assume that your purchases will grow $4\%$ a year forever.$)$c$.$ How would your answer change if this change caused your bond rating to drop one notch and your cost of capital to increase?