A small cubical block is placed on a triangular block M so that ,they touch each other along a smooth inclined contact plane as shown. The, inclined surface makes an angle `theta` With the horizontal. A hqrizontal force F is to be applied on the block mi so that the two bodies move without slipping against each other. Assuming the floor to be smooth also, determine the

(a) normal force with which m and M press against each other and
(b) the magnitude of external force F. Express your answer in terms of m, M, `theta` and `g`.