In order to make some additional money during your BBA, you have decided to create a micro$-$firm that makes home$-$made cookies. You have a manual mixer, a tray with a capacity of $12$ cookies and an oven to bake the cookies. The mixer has a maximal capacity equivalent to three dozen cookies and the oven has a capacity of one tray $(12$ cookies$).$ Key times are as follows:

$-$ Preparation of dough using the manual mixer $=6$ minutes $(*)$

$-$ Preparation of $12$ cookies using the dough and colocation in the tray $=2$ minutes $(*****)$

$-$ Oven set$-$up $=1$ minute $(**)$

$-$ Baking of cookies $=9$ minutes

$-$ Cooling of twelve cookies in a special unlimited area $=5$ minutes $(***)$

$-$ Colocation of twelve cookies in a box $=2$ minutes $(*****)$

$-$ Receive payment from customer $=1$ minute $(****)$

$(*)$ This activity requires the permanent presence of the operator

$(**)$ This activity requires the permanent presence of operator and it has to be made before each baking.

$(***)$ This activity occurs out of the tray and the transfer time between the tray and the cooling area can be considered as zero.

$(****)$ This activity occurs always at the end of the process and requires the permanent presence of the operator

$(*****)$ requires a permanent operator

Analyze the following issues:

For question $4,$ assume that you work alone AND that you have two trays.

$4.$ How many batches of three equal dozens for the same customer can you produce and sell working during four consecutive hours? Take into account the starting and closing times.