In​ 1920, the record for a certain race was 46.4 sec. In ​1970, it was 45.4 sec. Let ​R(t)=the record in the race and t= the number of years since 1920.
​a) Find a linear function that fits the data.
​b) Use the function in​ (a) to predict the record in 2003 and in 2006.
​c) Find the year when the record will be sec.