Properties of cuboids

How many edges does a cuboid have?

A solid is built from $7$ unit cubes. The bottom layer is a row of $4$ cubes. A second layer of $2$ cubes sits on top of the left two cubes of the bottom row. A third layer of $1$ cube sits on top of the leftmost cube of the second layer. Looking straight down from above, how many squares do you see?

Lena builds a staircase from unit cubes. From the front you see three columns side by side: the left column is $3$ cubes tall, the middle is $2$ cubes tall, and the right is $1$ cube tall. The staircase is $2$ cubes deep from front to back, and every column is the same height at the back as at the front. How many cubes did Lena use?