Great Product, Ltd$.$ has just received an order for $140$ Whozats, which must be ready for delivery at the start of week #$6.$ An MRP planner has prepared the following table showing product structure, lead times $($orders are lot$-$for$-$lot$),$ and quantities on hand:

$\backslash$table$[[$WHOZAT PARTS LIST,LEAD TIME,ON HAND$],[$Whozat$,1$ week,$15],[$Whatzat $(1),2$ weeks,$30],[$Wherezat $(5),1$ week,$56]]$

N$.$B$.$: A Whozat is composed of $1$ Whatzat$($s$).$ A Whatzat is composed of $5$ Wherezat$($s$).$

How many Wherezats should be ordered?