13. a biologist has found that the number of branches on a certain rare tree
in its first few years of life can be modeled by the polynomial
b(y) = 4y + y. the number of leaves on each branch can be modeled
by the polynomial (y) = 2y+3y + y, where y is the number of years
after the tree reaches a height of 6 feet. write a polynomial describing
the total number of leaves on the tree.