Remember that
The simple interest formula is equal to
where
I is the Final Interest Value
P is the Principal amount of money to be invested
r is the rate of interest
t is Number of Time Periods
in this problem we have
I=$55
r=2.8%=2.8/100=0.028
t=14/12=7/6 years
substitute given values
solve for P
P=$1,683.67