% Find all parts with class 'HW' or 'SG'
list := select (class = 'HW' or class = 'SG') (part);

% Find orders using those parts
listOrders := list njoin orderLine;
% Match the orders to get orderDate and customerNum
t1 := listOrders njoin orders;
% Find customer name using customerNum
t2 := customer njoin (project customerNum, orderDate (t1));

% Display customer name and order date
answer := project customerName, orderDate (t2);