This table shows how the cost of Paco's birthday party depends on the number of guests. ​
​Cost of Paco's birthday party:
​Guests, ​4 8​ ​12
​Cost, ​20 ​40 ​ ?

​Determine the cost of having guests at the party.
A
The relationship is not directly proportional.
B
$60\$ 60$60
C
$80\$ 80$80
D
$120\$ 120$120