Find an optimal parenthesization of a matrix-chain product whose sequence of dimensions is <2, 10, 5, 12, 2, 20, 5, 4>. That is, the dimensions of each matrix in the sequence < A1, A2, A3, A4, A5, A6, A7> are listed below:

A1 = 2 10

A2 = 10 5

A3 = 5 12

A4 = 12 2

A5 = 2 20

A6 = 20 5

A7 = 5 4.