Two masses m 1 and m 2 are connected by a string of length . They are held in a horizontal plane at a height H above two heavy plates A and B made of different materials placed on the floor. Initially, the distance between the two masses is a < When the masses are released they fall freely and collide with the plates simultaneously. The coefficient of restitution for the collision of the first ball-plate pair is 0. 8 and for the second ball-plate pair is 0. 4. The time after the collision when the string becomes taut is