paul sells encyclopedias door - to - door . he earns $ 150 on every paycheck , regardless of how many sets he sells . in addition , he earns commission as follows : commission sales 10 % $ 0.00 - $ 1000.00 5 % $ 1000.01 - - - > he does not earn double commission . that is , if his sales are $ 12000 , he earns 10 % on the first $ 10000 and 5 % on the remaining $ 2000 . his largest paycheck of the year was $ 1320 . what were his sales for that pay period ?