At 40 kph for 1.75 hrs, A meets B at point 70 km from X ( lets call it E )
B thus travelled 35 km in 1.75 hrs giving speed of 20 kph.
A meets C after travelling 3 mins at 40 kph which would be 2 km, at point 72 km from X ( F ).
If a travelled at 20 kph and B at 22 kph they would meet at Z which is 50 km from X.
C thus covered distance of 22 km ( F to Z ) in 57 mins, giving speed of 23.157894.... kph