Nina is an artist who sells paintings online. She
charges the same amount to ship each painting.
• When she sells 4 paintings, she charges a total of
$9.96 for shipping.
• When she sells 8 paintings, she charges a total of
$19.92 for shipping.
How much more does Nina charge for shipping 20
paintings than for shipping 16 paintings?

A. $2.49
B. $9.96
C. $19.92
D. $29.96