A simple pendulum crosses the highest point of a vertical circle with critical speed. What will be  the centripetal acceleration of the bob, when the string is horizontal?

if it is critical velocity then at the lowest point it is 5gl at the horizontal position it will be 3gl from conservation of energy 12mv20=12mv2+ mgl    ⇒12m5gl-mgl = 32mgl =12mv2   centrepetal acceleration v2l= 3g