A body A, of mass m= 0.1kg has an initial velocity of 3i∧ms−1 . It collides elastically with another body, B of the same mass which has an initial velocity of  5j∧ms−1 . After collision, A moves with a velocity v→=4i∧+j∧ . The energy of B after collision is written as x10J . the value of x is _________