Now why is all of this a useful exercise to go through? Well, now we are really ready to solve the question because in general, if we're talking about any triangle, we know that area is equal to 1 1 2 base times height. Now in this situation, area and our base and our height, they're all going to be functions of t. So we could write a of t is equal to 1 1 2 times b of t times h of t. And if we wanna find the rate of change of our area at that instant, and the instant that they're talking about is at time t sub zero, well then what we would wanna do is take the derivative of both sides with respect to t. So the derivative on the left-hand side with respect to t would be a prime of t, and then on the right-hand side, it would be 1 1 2 times, and we would actually use a combination of, well, it's really just the product rule right over here, the derivative of the first function with respect to t, so it's b prime of t times the second function. This is just the product rule here, plus the first function, b of t, times the derivative of the second function with respect to time. And we need to figure out not just the general expression, they want us to know what the rate of change of the area, so a prime of t at that instant, at t sub zero. So what we wanna figure out, we wanna figure out a prime at time t sub zero. Well, that's just going to be equal to 1 1 2 times b prime of t sub zero times h of t sub zero plus b of t sub zero times h prime of t sub zero.