A particle moves in a straight line from `A` to `B`
(a) for the first half of distance with speed `v_(1)` and the next half of distance with speed `v_(2)`.
(b) for the first one-third distance with speed `v_(1)` and the next two-third distance with speed `v_(2)`.
(c ) for the first one-fourth distance with speed `v_(0)`, the next half of distance with speed `2v_(0)` and the last one-fourth distance with speed `3v_(0)`.
Find the average speed in each case.