A rod of length L has non-uniform linear mass density given by ρ(x)=a+b(Lx)2 , where a and b are constants and 0≤x≤L . The value of x for the centre of mass of the rod is at:
a. 23(2a+ba+b)L
b. 43(3a+b2a+b)L
c. 34(2a+3ba+b)L
d. 23(3a+b2a+b)L