Annual sales (in millions of units) of a certain model of phone are expected to grow in accordance with the function
f(t) = 0.3t² +0.14t + 5.1 where t is measured in years, with t = 0 corresponding to the year 2018. Which of the following integrals would be used to determine the average number of phones sold over the 4-year period from 2019 to 2023?