DAX Count of Stores that are under the Average

Hi there,

I am struggleing with a DAX Measure, I would like to count the number of Stores that are under the average sales amount.

I am the following supporting DAX Measures.

This Year To Date Units

TYTD Units = TOTALYTD(CALCULATE([Total Units]),'CALENDAR'[DATE])

Number of Unique Stores/Sites

Site Count = CALCULATE(DISTINCTCOUNT(MASTER_SITE[STORE NAME]))

The average Unit Sales (This Year To Date)

TYTD Store Average (U) = DIVIDE([TYTD Units],[Site Count],0)

So the result I am looking for is the distinct count of Stores/Sites that are under the average Unit sales.