Please answer the question on the picture. Thank you.

Often on a topographic map, every fifth contour line is darkened. what is this line called? a. key b.slope c.benchmark d. index contour

Turbo the snail moves across the ground at a pace of 12 feet per day. if the garden is 48 feet away, how many days will it take for the snail to get there?

Ineed ! i have no clue how to do this problem.