Question 108305
I'm assuming compound interest, annually for 4 years.
{{{A=P(1+r)^t}}}
Where A is the value at the end of 4 years. 
{{{5000+400=5000(1+r)^t}}}A equals original amount plus interest. 
{{{5400=5000(1+r)^4}}}Divide both sides by 5000.
{{{1.08=(1+r)^4}}}Simplify.
{{{1.0194=1+r}}}Take the fourth root of both sides. 
{{{r=.0194}}}
The interest rate is 1.94%.