In casting experiments performed using a certain alloy and type of sand mould, it took 155 sec for a cube-shaped casting to solidify. The cube was 50 mm on a side. Find out the value of the mould constant (in sec/mm2 unit) using chvorinov's rule.

17 a tourist was planning a trip by car for travelling at some constant speed for 2.5 hours. however, he found that if he increases the speed by 20 km/h he can cover the same distance in 30 minutes less time than it was planned. what was the planned speed of the tourist, in km/h?