Final answer:
The expression for the rate of change of depth at 3 minutes is given by d'(3).
Step-by-step explanation:
The rate at which the depth of the rain puddle is changing with respect to time can be expressed using the derivative. Let d(t) be the depth of the puddle at time t. The expression for the rate of change of depth at 3 minutes is given by:
d'(3)