2. A table of numbers with 20 rows and 15 columns, $A_{1}, \ldots, A_{20}$ are the sums of the numbers in the rows, $B_{1}, \ldots, B_{15}$ are the sums of the numbers in the columns.

a) Is it possible that $A_{1}=\cdots=A_{20}=B_{1}=\cdots=B_{15}$?

b) If the equalities in part a) are satisfied, what is the sum $A_{1}+\cdots+A_{20}+$ $B_{1}+\cdots+B_{15}?$