Carlotta hand-paints T-shirts and sells them to her friends. She uses the equations below to determine her costs to produce shirts and the amount of money earned when she sells the shirts.

Production Cost: [tex]c = 28 + 3.5s[/tex], where [tex]c[/tex] is the total cost and [tex]s[/tex] is the number of shirts.

Money Earned: [tex]m = 10s[/tex], where [tex]m[/tex] is the amount of money earned from sales and [tex]s[/tex] is the number of shirts.

How many shirts must Carlotta sell to make a profit?

A. 2
B. 3
C. 4
D. 5



Answer :

To determine how many shirts Carlotta must sell to make a profit, we need to consider her costs and potential earnings. Let’s break down the problem step by step:

1. Understand the Production Cost Equation:
[tex]\[ c = 28 + 35s \][/tex]
Here, [tex]\(c\)[/tex] is the total cost and [tex]\(s\)[/tex] is the number of shirts produced.

- [tex]\(28\)[/tex] is the fixed cost (constant, regardless of how many shirts she produces).
- [tex]\(35s\)[/tex] is the variable cost (dependent on the number of shirts produced).

2. Understand the Money Earned Equation:
[tex]\[ m = 10s \][/tex]
Here, [tex]\(m\)[/tex] is the amount of money earned from selling [tex]\(s\)[/tex] shirts.

3. Determine the Profit Condition:
Carlotta makes a profit if the money earned is greater than the total production cost.
[tex]\[ m > c \][/tex]
Substituting the given equations, we get:
[tex]\[ 10s > 28 + 35s \][/tex]

4. Isolate [tex]\(s\)[/tex] to find the break-even point:
Rearrange the inequality:
[tex]\[ 10s - 35s > 28 \][/tex]
[tex]\[ -25s > 28 \][/tex]

5. Solve for [tex]\(s\)[/tex]:
[tex]\[ s < -\frac{28}{25} \][/tex]
[tex]\[ s < -1.12 \][/tex]

This result is nonsensical because you can’t sell a negative number of shirts, so let's re-examine where we start checking the number of shirts sold to make a profit.

6. Calculate specific values to check profitability:

Let’s test the given shirt counts (2, 3, 4, 5):

- For [tex]\( s = 2 \)[/tex]:
[tex]\[ \text{Total Cost} = 28 + 35 \times 2 = 28 + 70 = 98 \][/tex]
[tex]\[ \text{Money Earned} = 10 \times 2 = 20 \][/tex]
Since [tex]\( 20 < 98 \)[/tex] no profit is made.

- For [tex]\( s = 3 \)[/tex]:
[tex]\[ \text{Total Cost} = 28 + 35 \times 3 = 28 + 105 = 133 \][/tex]
[tex]\[ \text{Money Earned} = 10 \times 3 = 30 \][/tex]
Since [tex]\( 30 < 133 \)[/tex] no profit is made.

- For [tex]\( s = 4 \)[/tex]:
[tex]\[ \text{Total Cost} = 28 + 35 \times 4 = 28 + 140 = 168 \][/tex]
[tex]\[ \text{Money Earned} = 10 \times 4 = 40 \][/tex]
Since [tex]\( 40 < 168 \)[/tex] no profit is made.

- For [tex]\( s = 5 \)[/tex]:
[tex]\[ \text{Total Cost} = 28 + 35 \times 5 = 28 + 175 = 203 \][/tex]
[tex]\[ \text{Money Earned} = 10 \times 5 = 50 \][/tex]
Since [tex]\( 50 < 203 \)[/tex] no profit is made.

From testing the above values, it is clear that no profit is made with 2, 3, 4, or 5 shirts.

Conclusion:
No profit can be made with 2 to 5 shirts. Carlotta must sell more than 5 shirts to make a profit.