Oiling the chain will cause less friction between the gears and the chain. The bike was most likely had to pedal because more force was needed due to the friction caused between the chain and gears.
*First you want to find out how much he makes a day 15x2=30 *so for 2 weeks he made $30 a day *Obliviously there are 7 days a week so 7x2=14 *Now multiply 14x30= $420 hope I helped!