Shivam travels 360 km in 15 hours at the speed of 'a + b' km/hr. If he had increased his speed by b(>0) km/hr, it would have taken him 'b/2' hours less to complete the journey. What is the time taken by him to cover a distance of 198 km at the speed of 'a - b' km/hr?
1
10.5 hours
2
12.5 hours
3
14.5 hours
4
16.5 hours