Accumulation of Interest is related to the Force of Interest that you have been given.
[math]a(s) = exp\left(\int\limits_{0}^{s}\delta(t)\;dt\right)[/math]
"s" is in years. Compute the integral and you're on your way. Obviously, some definitions are irrational, so if you cannot calculate the value of the integral, or the related exponential, you have to rethink it.