Final answer:
The exponential function for $1000 with an 11% decay rate is represented as 1000(1-0.11)^t, which is option b in the given choices.
Step-by-step explanation:
To write an exponential function for a quantity starting at $1000 with an 11% decay rate, we need to represent the decay as a decrease from the whole (100%). Since 100% - 11% is 89%, or 0.89 in decimal form, the decay factor per time period (t) is 0.89. The exponential decay function is therefore represented as A(t) = A0(decay factor)t, where A0 is the initial amount. Thus, the correct formula is 1000(1-0.11)t, which corresponds to option b). The other options represent different scenarios of growth or decay which do not match the situation described.