Use the information above to answer questions 19 and 20.

July 30 Closing stock 100 units at N90
July 8 Purchased 200 units at N95
July 10 Sold 160 units
July 17 Returned 80 faulty units purchased at N95
July 18 Purchased 200 units at N105
July 20 Sold 180 units
July 28 Purchased 200 units at N110
July 29 Sold 120 units
July 30 Sold 100 units

How many units were at hand as at July 30?