Which among average speed and average velocity can be positive,negative or zero?

$A$ person walks along a straight road from his house to a market $2.5 \,km$ away with a speed of $5 \,km/h$ and instantly turns back and reaches his house with a speed of $7.5 \,km/h$. The average speed of the person during the time interval $0$ to $50 \,min$ is (in $m/s$)

Give the difference between average speed and average velocity.

The position $(x)$-time $(t)$ graph for a particle moving along a straight line is shown in the figure. The average speed of the particle in the time interval $t=0$ to $t=8 \, s$ is .......... $m/s$.

$A$ body moves with velocities $v$,$2v$,and $3v$ in the first,second,and third one-third distances of the path traveled,respectively. Its average speed is:

$A$ car travels from point $A$ to point $B$ with a speed of $40 \ km/h$ and returns from $B$ to $A$ with a speed of $60 \ km/h$. What is the average speed of the car for the entire journey (in $km/h$)?