a$.$ Plot the three$-$month U$.$S$.$ Treasury bill interest rate $($FRED code: TB$3$MS$)$ from $1960$ to present. What long$-$run pattern do you observe? What may have caused this pattern?

Hint: Enter $$TB$3$MS$$ into the FRED search box. To alter the start date, use the box for the starting observation date $($to the left of the $$Edit Graph$$ button$)$ to select the desired date.