Determine the number of cycles per day and the production quantity per cycle for this set of vehicles; use the sequence a-b-c-d.

a) 3 cycles, 12, 15, 3, 21
b) 4 cycles, 21, 12, 15, 3
c) 4 cycles, 15, 3, 21, 12
d) 3 cycles, 21, 12, 3, 15