Suppose both the average flow rate and average flow time of a process are increased by $50\%($e$.$g$.$ an average flow time of $20$ hours becomes $30$ hours after the $50\%$ increase$).$ What will be the percentage change in the average number of units in the process?

Notes: The number of units in process corresponds to the inventory, "I".

When "I" changes from I$\_$old to I$\_$new, the percentage change in "I" is given by $[($I$\_$new $-$ I$\_$old$)/$I$\_$old$]$x$100\%.$