I have a question from my AI course..

Consider a $100$ X $100$ grid world. The agent's task is to get to a goal object. The agent can move to any of its $4$ neighboring locations $($up$,$ down, left and right$)$ by exactly $1$ step. The agent has a sensor that it can use to perceive the brightness its current location. The location with the goal object has a brightness value of $0.$ Locations that are $5$ steps or less away will have a brightness value of $5.$ Locations that are $6$ to $10$ steps away will have a brightness value of $10.$ All other locations will have a brightness value of $15.$

a$)$ Analyze the environment type.

b$)$ Come up with a maximally admissible heuristic which only uses the brightness value from the sensor to estimate the distance to goal from current$$location

Kindly help me solve this question.. thank you so much