Math Snap

STEP 1

1. The cost of model $A$ is $39.
2. The cost of model $B$ is $21.
3. The fixed costs are $640.
4. The total cost function is given by $C(x, y) = 640 + 39x + 21y$.
5. We need to find $C(56, 60)$.

STEP 2

1. Substitute the given values into the cost function.
2. Calculate the total cost.

STEP 3

Substitute $x = 56$ and $y = 60$ into the cost function $C(x, y) = 640 + 39x + 21y$.
$$C(56, 60) = 640 + 39(56) + 21(60)$$

Calculate the total cost by evaluating the expression.
First, calculate $39 \times 56$:
$$39 \times 56 = 2184$$ Next, calculate $21 \times 60$:
$$21 \times 60 = 1260$$ Now, add these results to the fixed cost:
$$C(56, 60) = 640 + 2184 + 1260$$ $$C(56, 60) = 4084$$ The total cost is:
$\boxed{4084}$