See in the picture that the number of levels is clearly $1+\log_{4/3} n$. so,the total cost should be $cn(1+\log_{4/3} n)$ However in clrs and Khan Academy article of Cormen they are doing $cn\log_{4/3} n$,and saying levels are $\log_{4/3} n$.
Can anyone make me understand this? Got struck since many days.