CALC QUESTION: 2 cars, A going East @ 30mph & B going North @ 22.5mph are heading to I...?

Question

CALC QUESTION: 2 cars, A going East @ 30mph & B going North @ 22.5mph are heading to I. At what rate is the angle IAB changing at the instant when cars A and B are 300ft & 400ft, respectively, from the intersection?

Don't just solve it.
I need to know how to do the problem.
Help would be plenty appreciated.

Answer 1

As long as A and B are going in a straight line towards a fixed point, the angle never changes.

The angle would only change if the cars are moving in a direction other than towards I.

Answer 2

sorry maths is not my forte