Current Attempt in Progress

In its first month of operations, Lily Company made three purchases of merchandise in the following sequence:

$(1)310$ units at $$8,(2)450$ units at $$9,$ and $(3)240$ units at $$10.$

$($a$)$

Calculate the average unit cost. $($Round answer to $2$ decimal places, e$.$g$.15\mathrm{.}25.)$

Average unit cost $