c
અહી,દરેક પુસ્તકનું દાળ સમાન છે. 

\({{\text{m}}_{\text{1}}}\, = \,\,{m_2}\,\, = \,\,{m_3}\, = \,\,\,{m_4}\,\, = \,\,m\)

પુસ્તક 1 માટે \({{\text{x}}_{\text{1}}}\, = \,\,\frac{L}{2};\,\,\,\) પુસ્તક 2 માટે \({{\text{x}}_{\text{2}}}\, = \,\,\frac{L}{2}\,\, + \,\,\frac{L}{4}\,\, = \,\,\frac{{3L}}{4}\)

પુસ્તક 3 માટે \({{\text{x}}_{\text{3}}}\, = \,\,\frac{{3L}}{4}\,\, + \,\,\frac{L}{4}\,\, = \,\,L;\,\) પુસ્તક 3 માટે \({{\text{x}}_{\text{4}}}\, = \,\,L\, + \,\,\frac{L}{4}\,\, = \,\,\frac{{5\,L}}{4}\)

\(  \therefore \,\,{x_{cm}}\, = \,\,\,\frac{{{m_1}{x_1}\, + \,\,{m_2}{x_2}\, + \,\,{m_3}{x_3}\, + \,\,{m_4}{x_4}}}{{{m_1}\,\, + \,\,{m_2}\,\, + \,\,{m_3}\, + \,\,{m_4}}} \)

\(   = \,\,\,\frac{{m\left( {\frac{L}{2}} \right)\,\, + \,\,m\left( {\frac{{3\,L}}{4}} \right)\,\, + \,\,m\,(L)\,\, + \,\,m\left( {\frac{{5\,L}}{4}} \right)}}{{m\,\, + \,\,m\,\, + \,\,m\,\, + \,\,m}}  \)

\( = \,\,\frac{{3.5}}{4}\,L\,\,\,\, = \,\,0.875\,\,L\)