The formula is x (the amount)=10000(1+r)t, where r is the quarterly rate and t the time in quarters.
r=4% per annum=4%/4=1% quarterly, so r=0.01. 1+r=1.01=eln(1.01).
x=10000(1.01)t=10000etln(1.01),
dx/dt=10000ln(1.01)etln(1.01)=10000ln(1.01)(1.01)t. This is the rate of change at time t quarters.
At 35 years, t=140 quarters. dx/dt=10000ln(1.01)(1.01)140=400.71.
If the amount was dollars, then dx/dt is dollars/quarter. So in this case after 35 years, the rate of change is about $400 per quarter. In other words, the next quarter will see another $400 added to the amount.
After 35 years the original 10000 would have become 40271, so the rate of change is about 1%. ln(1.01) is about 0.01 or 1%.