There are 6 pencils brand Steadler and x pencils brand Faber Castell in a box. Given that the total pencils in a box are more than 10. Ayu takes a pencil out of the box and put a side. She then, takes another pencil and put a side. The probability that she takes two pencils from the same brand is
.
a) Illustrate the information above in a complete tree diagram.
b) Find the total number of pencils in a box.​