Apples can be harvested by hand or machine. Handpicking yields 60 pounds per hour, mechanical pickers yield 90 pounds per hour. If the wage rate of human pickers is $8 an hour and the rental on a mechanical picker is $15 an hour,
(a) Elucidate which is more cost-effective?
(b) If the salary rate increased to $12 an hour, which would be more cost-effective?