Annual sales (in millions of units) of a certain brand of tablet computers are expected to grow in accordance with the function

f(t) = 0.18t² + 0.16t + 2.64 (0 t 4)

per year, where t is measured in years, with

t = 0

corresponding to 1997. How many tablet computers will be sold over the 4 year period between the beginning of 1997 and the end of 2000? (Round your answer to two decimal places.)