A specially designed assault rifle can fire 36 rounds in 30 seconds. A commando starts firing at a target at time t = 0. At t = 15 sec and t = 30 sec, one commando each joins in. The target finally collapses at t = 65 sec. Assuming that 75% of the bullets fired hit the target & infinite bullets exist in the rifles magazines, find the total number of bullets striking the target till the moment it collapsed.