$(15)$ Consider an aisle in a distribution center. Pallets are stored in pallet rack. The lowest position in the rack $($floor level$)$ is used to pick individual cases by order pickers who place the cases into their carts. Pallets are $4\text{'}$ wide and are stored on both sides of the aisle. The aisle has $20$ pallet positions on each side. Pickers make one traversal of the aisle to access both sides. The following data is available from the past month.

$\backslash$table$[[$SKU$,$Pallet Positions in Aisle,$\backslash$table$[[$Average # Cases on Top$],[$Level of Pallet$]],$Picks$],[A,8,2\mathrm{.}5,50],[B,3,3,33],[C,2,1\mathrm{.}5,27],[D,12,3\mathrm{.}5,89],[E,7,2,8],[F,5,2\mathrm{.}5,27],[G,3,3,21]]$

a$.(5)$ How many pick positions are on the pick face on average?

b$.(5)$ What is the SKU density?

c$.(5)$ What is the pick density over a month?