A particular parallel program computation requires 100 sec when executed on single processor. If 40% of this computation is inherently sequential (i.e. will not benefit from additional processors), then theoretically best possible elapsed times of this program running with 2 and 4 processors, respectively, are

A

20 sec and 10 sec

B

30 sec and 15 sec

C

50 sec and 2 5 sec

D

70 sec and 55 sec