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1.05%.

Step-by-step explanation:

If an amount of money, P, called the principal, is borrowed for a period of t years at an annual interest rate r, the amount of interest, I, is given by

I=PrtwhereIPrt=interest=principal=rate=time

The following information is given.  

IPt=$1,260=$30,000=4 years

Substituting the given information into the simple interest formula and solving for r gives

I1,2601,260=Prt=(30,000)(r)(4)=120,000r

Dividing both sides by 120,000 and then converting to a percent, we have

r=1,260120,000=0.0105=1.05%

Thus, David's annual interest rate was 1.05%.