Peter and Lois caught a Wombat Airlines flight from Adelaide to Mount Gambier, but were required to pay extra because their luggage was heavier than the airline normally allows. The airline charges a constant extra amount for each kilogram of luggage over the allowable limit. Peter paid an extra $60 and Lois paid an extra $100 because together they had 52 kg of luggage. Had peter been travelling by himself and taken the combined luggage he would have had to pay an extra $340. The maximum number of kg of luggage a person can take without paying the extra charge is? A 20 B 15 C 12 D 18 E 30