Dagestan is a province in the Russian Republic known for its hilly terrains. Kadirov, a cab driver, was travelling from city P to city Q (in Dagestan). The distance between the two cities P and Q is partly uphill, party downhill and party on level ground. It took Kadirov 140 minutes to travel from P to Q covering a total distance of 72 km. How much time (in minutes) did he take on his return journey from Q to P if the uphill speed, the downhill speed and the speed of the cab on level ground are 30 km/hr, 45 km/hr and 36 km/hr, respectively?