Daily demand for the ice creams at I$-$Scream parlor is normally distributed with a mean of $160$ quarts and a standard deviation of $100$ quarts. The owner has the ice cream supplied by a wholesaler who charges $$2$ per quart. The wholesaler charges a $$400$ delivery charge independent of order size. It takes $4$ days for an order to be supplied. The opportunity cost of capital to I$-$Scream is estimated to be $25\%$ per year. Assume $360$ days in the year. $[$Show all work$]$

$($C$)$ currently the owner orders $4000$ quarts of icecream when they have $1680$ quarts on hand. The average time spent by a quart of icecream at the parlor is: