Operating Surplus = Rent + Interest + Profit (before tax). Bonus is part of Compensation of Employees, not Operating Surplus.
First, find Profit Before Tax from PAT:
PAT=PBT×(1−tax rate)
30=PBT×(1−0.40)
PBT=30/0.60=50
Operating Surplus = 50 (Rent & Interest) + 50 (PBT) = Rs.100 Cr.