If Ras descended at an average of 60k/hour for 42k (0.7 hours - 42 minutes) and lost 1 minute every 10k to Savoldelli, then Savoldelli would do the 42 k in 0.7 hours - 0.0666 hours (4 minutes) = .6334 hours (38 minutes). 42k in 38 minutes is 66.3 k/hour.

Will Savoldelli descend at an avg speed of 6 k/hour faster than Ras? They will have to, if Ras ascends at 1k/hour or more faster than them.