Darius paid 8.5% sales tax when he bought a new phone for $100. What was the total price of his new phone? A. $108.05
B. $109
C. $105.50
D. $108.50

the answer to your question a or b but i am pretty sure it is b. i hope this : )

step-by-step explanation:

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value