Math question, barrels and minute

Question

Rain water is collected in a 350-L barrel. During one storm, the volume of water in the barrel

after 1 min was 65 L.

The volume after 5 min was 125 L.

Suppose water continues to be collected at this rate.

a) How many minutes will it take for the barrel to fill?

Answer 1

20 minutes to fill it up

(1,65), (5,125) has slope (125-65)/5-1= 60/4= 15

L = 15t + b plug in either point to solve for b

65 = 15 + b

b= 50

L=15t + 50

350 = 15t +50

15t = 300

t = 300/15 = 20 minutes to fill the 350 L barrel assuming a linear relation, with same rate of flow, 15L per minute