A notebook costs: 16.80 : 8 = 2.10 ($)

A pen costs: 15.25 : 5 = 3.05 ($)

Anna buys: 2.10 x 4 + 3.05 x 8 = 8.40 + 24.40 = 32.80 ($)

Anna received: 2 x 20 - 32.80 = 7.20 ($)

Benny buys: 5 x 2.10 + 10 x 3.05 = 10.50 + 30.50 = 41 ($)

Benny received: 2 x 20 - 41 = -1 ($)

=> Anna received more and more than: 7.20 + 1 = 8.20 ($)