4. (10 points) The interest rates charged by Madison Finance on auto loan for used cars over a certain 6-month period in 2014 are approximated by the function 1 r(t) t+ -3t+12 (0 St≤6) 12 where t is measured in months and r(t) is the annual percentage rate. What is the average rate on auto loans extended by Madison over the 6-month period?