Bigbasket sells $750$ units per month of Sunsilk shampoo sachets. The unit cost of a sachet is Rs$.11$ and the cost of placing an order is Rs$.64.$ Bigbasket uses an inventory carrying charge of $15\%$ per year. Determine the optimal order quantity, order frequency, and the annual cost of inventory management. If$,$ through automation of the purchasing process, the ordering cost can be cut to Rs$\mathrm{.}28,$ what will be the new economic order quantity, order frequency, and annual inventory management cost? Explain these results.

$[5]$