The second option is the correct one. m/s^2
Answer:
<u><em>1000 units for breakeven</em></u>
Explanation:
Let x be the number of units sold at breakeven.
The total sales at the point would be $2x.
Variable costs would be $1x and fixed costs are $1000.
Total costs are = $1x + $1000
At breakeven: Sales = Costs
Sales =m Costs
$2x = $1x + $1000
$1x = $1000
x = 1000 units.
At 1000 units the sales are equal to the costs ("breakeven").
Weight of the carriage 
Normal force 
Frictional force 
Acceleration 
Explanation:
We have to look into the FBD of the carriage.
Horizontal forces and Vertical forces separately.
To calculate Weight we know that both the mass of the baby and the carriage will be added.
- So Weight(W)

To calculate normal force we have to look upon the vertical component of forces, as Normal force is acting vertically.We have weight which is a downward force along with
, force of
acting vertically downward.Both are downward and Normal is upward so Normal force 
- Normal force (N)

- Frictional force (f)

To calculate acceleration we will use Newtons second law.
That is Force is product of mass and acceleration.
We can see in the diagram that
and
component of forces.
So Fnet = Fy(Horizontal) - f(friction) 
- Acceleration (a) =

So we have the weight of the carriage, normal force,frictional force and acceleration.
Surface tension - My definition -
It's exactly what it says - The tension of a surface with a liquid (such as water), caused by the attraction of the surfaces layer ---- I hope this helps ---- I actually did research it and got some of this from a dictionary, but I changed some of it, too.... Sorry if this doesn't help :)