Planck's constant  h speed of light in vacuum c and Newton's gravitational constantG are three fundamental constants. Which of the following combinations of these has the dimension of length?

According to equation,l∝hpcqGrl=khpcqGr………(1)Writting dimensions of physical quantities on both sides, M0LT0=ML2 T-1pLT-1qM-1 L3 T-2rApplying the principle of homogeneity of dimensions, we getp-r=0……..(2)2 p+q+3 r=1…….(3)-p-q-2 r=0……….(4)Solving eqns. (2), (3) and (4), we getp=r=12,q=-32From eq (1) l=hGc3/2