Question $4$: A DC center uses a double order point system. Its replenishment orders come from the Central Supply. The weekly demand of the DC is $150$ units, the manufacturing lead time is $2$ weeks, and the replenishment lead time is $1$ week. If the safety stock is $30$ units, determine: $(2\mathrm{.}5$ marks$)$

$1-$ The stock level at which the DC provides a warning to the Central Supply

$2-$ The stock level at which the DC send the order to the Central Supply