$2-$ An object, M $=2$ kg on a frictionless horizontal surface was displaced along $+$ x$-$axis by d

$=(4$i$)$ m while a force F $=(8$i $+6$k$)$ N was acting on the object. Here, i and k are the unit

vectors along the x and z axis, respectively. $($a$)$ Find the work done by F on the object during

the displacement. What is the scalar product, F $.$ d$?($b$)$ If the object start from rest, vi $=0,$ find

it$$s kinetic energy at the end of this displacement. What is the work done by the gravitational

force during this displacement?