“…Fractional differential equations are generalizations of classical differential equations of integer order and have gained considerable importance due to their various field such as viscoelasticity, signal processing, rheology, control theory, probability, statistics and economics, robotics etc [7,10,11,17,19,22]. Recently, the theory of fractional differential equations and their applications have been attracting more and more attention in the literature [1,8,12,15,16].…”