[" (d) "(1)" and "(3)" ,respectively "],[" Two coaxial solenoids of different radii carry current "I" in "],[" the same direction.Let "bar(F)_(1)" be the magnetic force on the "],[" inner solenoid due the outer one and "vec F_(2)" be the magnetic "],[" force on the outer solenoid due to the inner one.Then "],[" (a) "vec F_(1)" is radially inwards and "vec F_(2)=0],[" (b) "vec F_(1)" is radially outwards and "vec F_(2)=0],[" (b) "vec F_(1)=vec F_(2)=0],[" (d) "vec F_(1)" is radially inwards and "vec F_(2)=0" is radially outwards "],[(2015)" ) "]