help please

Liz's fashion boutique is open 50 weeks a year and sells an average of 35 dresses week with a standard deviation of 10 dresses per week, at a retail price of $250 per dress. Every order costs $200 to process (no matter what the order size) and the wholesale cost is $69.00 per dress. Liz calculates her annual per-dress holding cost 20% of the wholesale cost. Calculate the Economic Order Quantity for dresses. (Whole dresses only, please)